Translate all code to English (#1836)

* Review the EN heading format.

* Fix pythontutor headings.

* Fix pythontutor headings.

* bug fixes

* Fix headings in **/summary.md

* Revisit the CN-to-EN translation for Python code using Claude-4.5

* Revisit the CN-to-EN translation for Java code using Claude-4.5

* Revisit the CN-to-EN translation for Cpp code using Claude-4.5.

* Fix the dictionary.

* Fix cpp code translation for the multipart strings.

* Translate Go code to English.

* Update workflows to test EN code.

* Add EN translation for C.

* Add EN translation for CSharp.

* Add EN translation for Swift.

* Trigger the CI check.

* Revert.

* Update en/hash_map.md

* Add the EN version of Dart code.

* Add the EN version of Kotlin code.

* Add missing code files.

* Add the EN version of JavaScript code.

* Add the EN version of TypeScript code.

* Fix the workflows.

* Add the EN version of Ruby code.

* Add the EN version of Rust code.

* Update the CI check for the English version  code.

* Update Python CI check.

* Fix cmakelists for en/C code.

* Fix Ruby comments

en/codes/javascript/.prettierrc

@@ -0,0 +1,6 @@
+{
+    "tabWidth": 4,
+    "useTabs": false,
+    "semi": true,
+    "singleQuote": true
+}

en/codes/javascript/chapter_array_and_linkedlist/array.js

@@ -0,0 +1,97 @@
+/**
+ * File: array.js
+ * Created Time: 2022-11-27
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Random access to element */
+function randomAccess(nums) {
+    // Randomly select a number in the interval [0, nums.length)
+    const random_index = Math.floor(Math.random() * nums.length);
+    // Retrieve and return the random element
+    const random_num = nums[random_index];
+    return random_num;
+}
+
+/* Extend array length */
+// Note: JavaScript's Array is dynamic array, can be directly expanded
+// For learning purposes, this function treats Array as fixed-length array
+function extend(nums, enlarge) {
+    // Initialize an array with extended length
+    const res = new Array(nums.length + enlarge).fill(0);
+    // Copy all elements from the original array to the new array
+    for (let i = 0; i < nums.length; i++) {
+        res[i] = nums[i];
+    }
+    // Return the extended new array
+    return res;
+}
+
+/* Insert element num at index index in the array */
+function insert(nums, num, index) {
+    // Move all elements at and after index index backward by one position
+    for (let i = nums.length - 1; i > index; i--) {
+        nums[i] = nums[i - 1];
+    }
+    // Assign num to the element at index index
+    nums[index] = num;
+}
+
+/* Remove the element at index index */
+function remove(nums, index) {
+    // Move all elements after index index forward by one position
+    for (let i = index; i < nums.length - 1; i++) {
+        nums[i] = nums[i + 1];
+    }
+}
+
+/* Traverse array */
+function traverse(nums) {
+    let count = 0;
+    // Traverse array by index
+    for (let i = 0; i < nums.length; i++) {
+        count += nums[i];
+    }
+    // Direct traversal of array elements
+    for (const num of nums) {
+        count += num;
+    }
+}
+
+/* Find the specified element in the array */
+function find(nums, target) {
+    for (let i = 0; i < nums.length; i++) {
+        if (nums[i] === target) return i;
+    }
+    return -1;
+}
+
+/* Driver Code */
+/* Initialize array */
+const arr = new Array(5).fill(0);
+console.log('Array arr =', arr);
+let nums = [1, 3, 2, 5, 4];
+console.log('Array nums =', nums);
+
+/* Insert element */
+let random_num = randomAccess(nums);
+console.log('Get random element in nums', random_num);
+
+/* Traverse array */
+nums = extend(nums, 3);
+console.log('Extend array length to 8, get nums =', nums);
+
+/* Insert element */
+insert(nums, 6, 3);
+console.log('Insert number 6 at index 3, get nums =', nums);
+
+/* Remove element */
+remove(nums, 2);
+console.log('Remove element at index 2, get nums =', nums);
+
+/* Traverse array */
+traverse(nums);
+
+/* Find element */
+let index = find(nums, 3);
+console.log('Find element 3 in nums, get index =', index);

en/codes/javascript/chapter_array_and_linkedlist/linked_list.js

@@ -0,0 +1,82 @@
+/**
+ * File: linked_list.js
+ * Created Time: 2022-12-12
+ * Author: IsChristina (christinaxia77@foxmail.com), Justin (xiefahit@gmail.com)
+ */
+
+const { printLinkedList } = require('../modules/PrintUtil');
+const { ListNode } = require('../modules/ListNode');
+
+/* Insert node P after node n0 in the linked list */
+function insert(n0, P) {
+    const n1 = n0.next;
+    P.next = n1;
+    n0.next = P;
+}
+
+/* Remove the first node after node n0 in the linked list */
+function remove(n0) {
+    if (!n0.next) return;
+    // n0 -> P -> n1
+    const P = n0.next;
+    const n1 = P.next;
+    n0.next = n1;
+}
+
+/* Access the node at index index in the linked list */
+function access(head, index) {
+    for (let i = 0; i < index; i++) {
+        if (!head) {
+            return null;
+        }
+        head = head.next;
+    }
+    return head;
+}
+
+/* Find the first node with value target in the linked list */
+function find(head, target) {
+    let index = 0;
+    while (head !== null) {
+        if (head.val === target) {
+            return index;
+        }
+        head = head.next;
+        index += 1;
+    }
+    return -1;
+}
+
+/* Driver Code */
+/* Initialize linked list */
+// Initialize each node
+const n0 = new ListNode(1);
+const n1 = new ListNode(3);
+const n2 = new ListNode(2);
+const n3 = new ListNode(5);
+const n4 = new ListNode(4);
+// Build references between nodes
+n0.next = n1;
+n1.next = n2;
+n2.next = n3;
+n3.next = n4;
+console.log('Initialized linked list is');
+printLinkedList(n0);
+
+/* Insert node */
+insert(n0, new ListNode(0));
+console.log('Linked list after inserting node is');
+printLinkedList(n0);
+
+/* Remove node */
+remove(n0);
+console.log('Linked list after removing node is');
+printLinkedList(n0);
+
+/* Access node */
+const node = access(n0, 3);
+console.log('Value of node at index 3 in linked list = ' + node.val);
+
+/* Search node */
+const index = find(n0, 2);
+console.log('Index of node with value 2 in linked list = ' + index);

en/codes/javascript/chapter_array_and_linkedlist/list.js

@@ -0,0 +1,57 @@
+/**
+ * File: list.js
+ * Created Time: 2022-12-12
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Initialize list */
+const nums = [1, 3, 2, 5, 4];
+console.log(`List nums = ${nums}`);
+
+/* Update element */
+const num = nums[1];
+console.log(`Access element at index 1, get num = ${num}`);
+
+/* Add elements at the end */
+nums[1] = 0;
+console.log(`Update element at index 1 to 0, get nums = ${nums}`);
+
+/* Remove element */
+nums.length = 0;
+console.log(`After clearing list, nums = ${nums}`);
+
+/* Direct traversal of list elements */
+nums.push(1);
+nums.push(3);
+nums.push(2);
+nums.push(5);
+nums.push(4);
+console.log(`After adding elements, nums = ${nums}`);
+
+/* Sort list */
+nums.splice(3, 0, 6);
+console.log(`Insert number 6 at index 3, get nums = ${nums}`);
+
+/* Remove element */
+nums.splice(3, 1);
+console.log(`Delete element at index 3, get nums = ${nums}`);
+
+/* Traverse list by index */
+let count = 0;
+for (let i = 0; i < nums.length; i++) {
+    count += nums[i];
+}
+/* Directly traverse list elements */
+count = 0;
+for (const x of nums) {
+    count += x;
+}
+
+/* Concatenate two lists */
+const nums1 = [6, 8, 7, 10, 9];
+nums.push(...nums1);
+console.log(`After concatenating list nums1 to nums, get nums = ${nums}`);
+
+/* Sort list */
+nums.sort((a, b) => a - b);
+console.log(`After sorting list, nums = ${nums}`);

en/codes/javascript/chapter_array_and_linkedlist/my_list.js

@@ -0,0 +1,141 @@
+/**
+ * File: my_list.js
+ * Created Time: 2022-12-12
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* List class */
+class MyList {
+    #arr = new Array(); // Array (stores list elements)
+    #capacity = 10; // List capacity
+    #size = 0; // List length (current number of elements)
+    #extendRatio = 2; // Multiple by which the list capacity is extended each time
+
+    /* Constructor */
+    constructor() {
+        this.#arr = new Array(this.#capacity);
+    }
+
+    /* Get list length (current number of elements) */
+    size() {
+        return this.#size;
+    }
+
+    /* Get list capacity */
+    capacity() {
+        return this.#capacity;
+    }
+
+    /* Update element */
+    get(index) {
+        // If the index is out of bounds, throw an exception, as below
+        if (index < 0 || index >= this.#size) throw new Error('Index out of bounds');
+        return this.#arr[index];
+    }
+
+    /* Add elements at the end */
+    set(index, num) {
+        if (index < 0 || index >= this.#size) throw new Error('Index out of bounds');
+        this.#arr[index] = num;
+    }
+
+    /* Direct traversal of list elements */
+    add(num) {
+        // If length equals capacity, need to expand
+        if (this.#size === this.#capacity) {
+            this.extendCapacity();
+        }
+        // Add new element to end of list
+        this.#arr[this.#size] = num;
+        this.#size++;
+    }
+
+    /* Sort list */
+    insert(index, num) {
+        if (index < 0 || index >= this.#size) throw new Error('Index out of bounds');
+        // When the number of elements exceeds capacity, trigger the extension mechanism
+        if (this.#size === this.#capacity) {
+            this.extendCapacity();
+        }
+        // Move all elements after index index forward by one position
+        for (let j = this.#size - 1; j >= index; j--) {
+            this.#arr[j + 1] = this.#arr[j];
+        }
+        // Update the number of elements
+        this.#arr[index] = num;
+        this.#size++;
+    }
+
+    /* Remove element */
+    remove(index) {
+        if (index < 0 || index >= this.#size) throw new Error('Index out of bounds');
+        let num = this.#arr[index];
+        // Create a new array with length _extend_ratio times the original array, and copy the original array to the new array
+        for (let j = index; j < this.#size - 1; j++) {
+            this.#arr[j] = this.#arr[j + 1];
+        }
+        // Update the number of elements
+        this.#size--;
+        // Return the removed element
+        return num;
+    }
+
+    /* Driver Code */
+    extendCapacity() {
+        // Create a new array with length extendRatio times the original array and copy the original array to the new array
+        this.#arr = this.#arr.concat(
+            new Array(this.capacity() * (this.#extendRatio - 1))
+        );
+        // Add elements at the end
+        this.#capacity = this.#arr.length;
+    }
+
+    /* Convert list to array */
+    toArray() {
+        let size = this.size();
+        // Elements enqueue
+        const arr = new Array(size);
+        for (let i = 0; i < size; i++) {
+            arr[i] = this.get(i);
+        }
+        return arr;
+    }
+}
+
+/* Driver Code */
+/* Initialize list */
+const nums = new MyList();
+/* Direct traversal of list elements */
+nums.add(1);
+nums.add(3);
+nums.add(2);
+nums.add(5);
+nums.add(4);
+console.log(
+    `List nums = ${nums.toArray()}, capacity = ${nums.capacity()}, length = ${nums.size()}`
+);
+
+/* Sort list */
+nums.insert(3, 6);
+console.log(`Insert number 6 at index 3, get nums = ${nums.toArray()}`);
+
+/* Remove element */
+nums.remove(3);
+console.log(`Delete element at index 3, get nums = ${nums.toArray()}`);
+
+/* Update element */
+const num = nums.get(1);
+console.log(`Access element at index 1, get num = ${num}`);
+
+/* Add elements at the end */
+nums.set(1, 0);
+console.log(`Update element at index 1 to 0, get nums = ${nums.toArray()}`);
+
+/* Test capacity expansion mechanism */
+for (let i = 0; i < 10; i++) {
+    // At i = 5, the list length will exceed the list capacity, triggering the expansion mechanism
+    nums.add(i);
+}
+console.log(
+    `After expansion, list nums = ${nums.toArray()}, capacity = ${nums.capacity()}, length = ${nums.size()}`
+);

en/codes/javascript/chapter_backtracking/n_queens.js

@@ -0,0 +1,55 @@
+/**
+ * File: n_queens.js
+ * Created Time: 2023-05-13
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Backtracking algorithm: N queens */
+function backtrack(row, n, state, res, cols, diags1, diags2) {
+    // When all rows are placed, record the solution
+    if (row === n) {
+        res.push(state.map((row) => row.slice()));
+        return;
+    }
+    // Traverse all columns
+    for (let col = 0; col < n; col++) {
+        // Calculate the main diagonal and anti-diagonal corresponding to this cell
+        const diag1 = row - col + n - 1;
+        const diag2 = row + col;
+        // Pruning: do not allow queens to exist in the column, main diagonal, and anti-diagonal of this cell
+        if (!cols[col] && !diags1[diag1] && !diags2[diag2]) {
+            // Attempt: place the queen in this cell
+            state[row][col] = 'Q';
+            cols[col] = diags1[diag1] = diags2[diag2] = true;
+            // Place the next row
+            backtrack(row + 1, n, state, res, cols, diags1, diags2);
+            // Backtrack: restore this cell to an empty cell
+            state[row][col] = '#';
+            cols[col] = diags1[diag1] = diags2[diag2] = false;
+        }
+    }
+}
+
+/* Solve N queens */
+function nQueens(n) {
+    // Initialize an n*n chessboard, where 'Q' represents a queen and '#' represents an empty cell
+    const state = Array.from({ length: n }, () => Array(n).fill('#'));
+    const cols = Array(n).fill(false); // Record whether there is a queen in the column
+    const diags1 = Array(2 * n - 1).fill(false); // Record whether there is a queen on the main diagonal
+    const diags2 = Array(2 * n - 1).fill(false); // Record whether there is a queen on the anti-diagonal
+    const res = [];
+
+    backtrack(0, n, state, res, cols, diags1, diags2);
+    return res;
+}
+
+// Driver Code
+const n = 4;
+const res = nQueens(n);
+
+console.log(`Input board size is ${n}`);
+console.log(`Total queen placement solutions: ${res.length}`);
+res.forEach((state) => {
+    console.log('--------------------');
+    state.forEach((row) => console.log(row));
+});

en/codes/javascript/chapter_backtracking/permutations_i.js

@@ -0,0 +1,42 @@
+/**
+ * File: permutations_i.js
+ * Created Time: 2023-05-13
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Backtracking algorithm: Permutations I */
+function backtrack(state, choices, selected, res) {
+    // When the state length equals the number of elements, record the solution
+    if (state.length === choices.length) {
+        res.push([...state]);
+        return;
+    }
+    // Traverse all choices
+    choices.forEach((choice, i) => {
+        // Pruning: do not allow repeated selection of elements
+        if (!selected[i]) {
+            // Attempt: make choice, update state
+            selected[i] = true;
+            state.push(choice);
+            // Proceed to the next round of selection
+            backtrack(state, choices, selected, res);
+            // Backtrack: undo choice, restore to previous state
+            selected[i] = false;
+            state.pop();
+        }
+    });
+}
+
+/* Permutations I */
+function permutationsI(nums) {
+    const res = [];
+    backtrack([], nums, Array(nums.length).fill(false), res);
+    return res;
+}
+
+// Driver Code
+const nums = [1, 2, 3];
+const res = permutationsI(nums);
+
+console.log(`Input array nums = ${JSON.stringify(nums)}`);
+console.log(`All permutations res = ${JSON.stringify(res)}`);

en/codes/javascript/chapter_backtracking/permutations_ii.js

@@ -0,0 +1,44 @@
+/**
+ * File: permutations_ii.js
+ * Created Time: 2023-05-13
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Backtracking algorithm: Permutations II */
+function backtrack(state, choices, selected, res) {
+    // When the state length equals the number of elements, record the solution
+    if (state.length === choices.length) {
+        res.push([...state]);
+        return;
+    }
+    // Traverse all choices
+    const duplicated = new Set();
+    choices.forEach((choice, i) => {
+        // Pruning: do not allow repeated selection of elements and do not allow repeated selection of equal elements
+        if (!selected[i] && !duplicated.has(choice)) {
+            // Attempt: make choice, update state
+            duplicated.add(choice); // Record the selected element value
+            selected[i] = true;
+            state.push(choice);
+            // Proceed to the next round of selection
+            backtrack(state, choices, selected, res);
+            // Backtrack: undo choice, restore to previous state
+            selected[i] = false;
+            state.pop();
+        }
+    });
+}
+
+/* Permutations II */
+function permutationsII(nums) {
+    const res = [];
+    backtrack([], nums, Array(nums.length).fill(false), res);
+    return res;
+}
+
+// Driver Code
+const nums = [1, 2, 2];
+const res = permutationsII(nums);
+
+console.log(`Input array nums = ${JSON.stringify(nums)}`);
+console.log(`All permutations res = ${JSON.stringify(res)}`);

en/codes/javascript/chapter_backtracking/preorder_traversal_i_compact.js

@@ -0,0 +1,33 @@
+/**
+ * File: preorder_traversal_i_compact.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Preorder traversal: Example 1 */
+function preOrder(root, res) {
+    if (root === null) {
+        return;
+    }
+    if (root.val === 7) {
+        // Record solution
+        res.push(root);
+    }
+    preOrder(root.left, res);
+    preOrder(root.right, res);
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log('\nInitialize binary tree');
+printTree(root);
+
+// Preorder traversal
+const res = [];
+preOrder(root, res);
+
+console.log('\nOutput all nodes with value 7');
+console.log(res.map((node) => node.val));

en/codes/javascript/chapter_backtracking/preorder_traversal_ii_compact.js

@@ -0,0 +1,40 @@
+/**
+ * File: preorder_traversal_ii_compact.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Preorder traversal: Example 2 */
+function preOrder(root, path, res) {
+    if (root === null) {
+        return;
+    }
+    // Attempt
+    path.push(root);
+    if (root.val === 7) {
+        // Record solution
+        res.push([...path]);
+    }
+    preOrder(root.left, path, res);
+    preOrder(root.right, path, res);
+    // Backtrack
+    path.pop();
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log('\nInitialize binary tree');
+printTree(root);
+
+// Preorder traversal
+const path = [];
+const res = [];
+preOrder(root, path, res);
+
+console.log('\nOutput all paths from root node to node 7');
+res.forEach((path) => {
+    console.log(path.map((node) => node.val));
+});

en/codes/javascript/chapter_backtracking/preorder_traversal_iii_compact.js

@@ -0,0 +1,41 @@
+/**
+ * File: preorder_traversal_iii_compact.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Preorder traversal: Example 3 */
+function preOrder(root, path, res) {
+    // Pruning
+    if (root === null || root.val === 3) {
+        return;
+    }
+    // Attempt
+    path.push(root);
+    if (root.val === 7) {
+        // Record solution
+        res.push([...path]);
+    }
+    preOrder(root.left, path, res);
+    preOrder(root.right, path, res);
+    // Backtrack
+    path.pop();
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log('\nInitialize binary tree');
+printTree(root);
+
+// Preorder traversal
+const path = [];
+const res = [];
+preOrder(root, path, res);
+
+console.log('\nOutput all paths from root node to node 7, paths do not include nodes with value 3');
+res.forEach((path) => {
+    console.log(path.map((node) => node.val));
+});

en/codes/javascript/chapter_backtracking/preorder_traversal_iii_template.js

@@ -0,0 +1,68 @@
+/**
+ * File: preorder_traversal_iii_template.js
+ * Created Time: 2023-05-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Check if the current state is a solution */
+function isSolution(state) {
+    return state && state[state.length - 1]?.val === 7;
+}
+
+/* Record solution */
+function recordSolution(state, res) {
+    res.push([...state]);
+}
+
+/* Check if the choice is valid under the current state */
+function isValid(state, choice) {
+    return choice !== null && choice.val !== 3;
+}
+
+/* Update state */
+function makeChoice(state, choice) {
+    state.push(choice);
+}
+
+/* Restore state */
+function undoChoice(state) {
+    state.pop();
+}
+
+/* Backtracking algorithm: Example 3 */
+function backtrack(state, choices, res) {
+    // Check if it is a solution
+    if (isSolution(state)) {
+        // Record solution
+        recordSolution(state, res);
+    }
+    // Traverse all choices
+    for (const choice of choices) {
+        // Pruning: check if the choice is valid
+        if (isValid(state, choice)) {
+            // Attempt: make choice, update state
+            makeChoice(state, choice);
+            // Proceed to the next round of selection
+            backtrack(state, [choice.left, choice.right], res);
+            // Backtrack: undo choice, restore to previous state
+            undoChoice(state);
+        }
+    }
+}
+
+// Driver Code
+const root = arrToTree([1, 7, 3, 4, 5, 6, 7]);
+console.log('\nInitialize binary tree');
+printTree(root);
+
+// Backtracking algorithm
+const res = [];
+backtrack([], [root], res);
+
+console.log('\nOutput all paths from root node to node 7, requiring paths do not include nodes with value 3');
+res.forEach((path) => {
+    console.log(path.map((node) => node.val));
+});

en/codes/javascript/chapter_backtracking/subset_sum_i.js

@@ -0,0 +1,46 @@
+/**
+ * File: subset_sum_i.js
+ * Created Time: 2023-07-30
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Backtracking algorithm: Subset sum I */
+function backtrack(state, target, choices, start, res) {
+    // When the subset sum equals target, record the solution
+    if (target === 0) {
+        res.push([...state]);
+        return;
+    }
+    // Traverse all choices
+    // Pruning 2: start traversing from start to avoid generating duplicate subsets
+    for (let i = start; i < choices.length; i++) {
+        // Pruning 1: if the subset sum exceeds target, end the loop directly
+        // This is because the array is sorted, and later elements are larger, so the subset sum will definitely exceed target
+        if (target - choices[i] < 0) {
+            break;
+        }
+        // Attempt: make choice, update target, start
+        state.push(choices[i]);
+        // Proceed to the next round of selection
+        backtrack(state, target - choices[i], choices, i, res);
+        // Backtrack: undo choice, restore to previous state
+        state.pop();
+    }
+}
+
+/* Solve subset sum I */
+function subsetSumI(nums, target) {
+    const state = []; // State (subset)
+    nums.sort((a, b) => a - b); // Sort nums
+    const start = 0; // Start point for traversal
+    const res = []; // Result list (subset list)
+    backtrack(state, target, nums, start, res);
+    return res;
+}
+
+/* Driver Code */
+const nums = [3, 4, 5];
+const target = 9;
+const res = subsetSumI(nums, target);
+console.log(`Input array nums = ${JSON.stringify(nums)}, target = ${target}`);
+console.log(`All subsets with sum equal to ${target} res = ${JSON.stringify(res)}`);

en/codes/javascript/chapter_backtracking/subset_sum_i_naive.js

@@ -0,0 +1,44 @@
+/**
+ * File: subset_sum_i_naive.js
+ * Created Time: 2023-07-30
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Backtracking algorithm: Subset sum I */
+function backtrack(state, target, total, choices, res) {
+    // When the subset sum equals target, record the solution
+    if (total === target) {
+        res.push([...state]);
+        return;
+    }
+    // Traverse all choices
+    for (let i = 0; i < choices.length; i++) {
+        // Pruning: if the subset sum exceeds target, skip this choice
+        if (total + choices[i] > target) {
+            continue;
+        }
+        // Attempt: make choice, update element sum total
+        state.push(choices[i]);
+        // Proceed to the next round of selection
+        backtrack(state, target, total + choices[i], choices, res);
+        // Backtrack: undo choice, restore to previous state
+        state.pop();
+    }
+}
+
+/* Solve subset sum I (including duplicate subsets) */
+function subsetSumINaive(nums, target) {
+    const state = []; // State (subset)
+    const total = 0; // Subset sum
+    const res = []; // Result list (subset list)
+    backtrack(state, target, total, nums, res);
+    return res;
+}
+
+/* Driver Code */
+const nums = [3, 4, 5];
+const target = 9;
+const res = subsetSumINaive(nums, target);
+console.log(`Input array nums = ${JSON.stringify(nums)}, target = ${target}`);
+console.log(`All subsets with sum equal to ${target} res = ${JSON.stringify(res)}`);
+console.log('Please note that this method outputs results containing duplicate sets');

en/codes/javascript/chapter_backtracking/subset_sum_ii.js

@@ -0,0 +1,51 @@
+/**
+ * File: subset_sum_ii.js
+ * Created Time: 2023-07-30
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Backtracking algorithm: Subset sum II */
+function backtrack(state, target, choices, start, res) {
+    // When the subset sum equals target, record the solution
+    if (target === 0) {
+        res.push([...state]);
+        return;
+    }
+    // Traverse all choices
+    // Pruning 2: start traversing from start to avoid generating duplicate subsets
+    // Pruning 3: start traversing from start to avoid repeatedly selecting the same element
+    for (let i = start; i < choices.length; i++) {
+        // Pruning 1: if the subset sum exceeds target, end the loop directly
+        // This is because the array is sorted, and later elements are larger, so the subset sum will definitely exceed target
+        if (target - choices[i] < 0) {
+            break;
+        }
+        // Pruning 4: if this element equals the left element, it means this search branch is duplicate, skip it directly
+        if (i > start && choices[i] === choices[i - 1]) {
+            continue;
+        }
+        // Attempt: make choice, update target, start
+        state.push(choices[i]);
+        // Proceed to the next round of selection
+        backtrack(state, target - choices[i], choices, i + 1, res);
+        // Backtrack: undo choice, restore to previous state
+        state.pop();
+    }
+}
+
+/* Solve subset sum II */
+function subsetSumII(nums, target) {
+    const state = []; // State (subset)
+    nums.sort((a, b) => a - b); // Sort nums
+    const start = 0; // Start point for traversal
+    const res = []; // Result list (subset list)
+    backtrack(state, target, nums, start, res);
+    return res;
+}
+
+/* Driver Code */
+const nums = [4, 4, 5];
+const target = 9;
+const res = subsetSumII(nums, target);
+console.log(`Input array nums = ${JSON.stringify(nums)}, target = ${target}`);
+console.log(`All subsets with sum equal to ${target} res = ${JSON.stringify(res)}`);

en/codes/javascript/chapter_computational_complexity/iteration.js

@@ -0,0 +1,70 @@
+/**
+ * File: iteration.js
+ * Created Time: 2023-08-28
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* for loop */
+function forLoop(n) {
+    let res = 0;
+    // Sum 1, 2, ..., n-1, n
+    for (let i = 1; i <= n; i++) {
+        res += i;
+    }
+    return res;
+}
+
+/* while loop */
+function whileLoop(n) {
+    let res = 0;
+    let i = 1; // Initialize condition variable
+    // Sum 1, 2, ..., n-1, n
+    while (i <= n) {
+        res += i;
+        i++; // Update condition variable
+    }
+    return res;
+}
+
+/* while loop (two updates) */
+function whileLoopII(n) {
+    let res = 0;
+    let i = 1; // Initialize condition variable
+    // Sum 1, 4, 10, ...
+    while (i <= n) {
+        res += i;
+        // Update condition variable
+        i++;
+        i *= 2;
+    }
+    return res;
+}
+
+/* Nested for loop */
+function nestedForLoop(n) {
+    let res = '';
+    // Loop i = 1, 2, ..., n-1, n
+    for (let i = 1; i <= n; i++) {
+        // Loop j = 1, 2, ..., n-1, n
+        for (let j = 1; j <= n; j++) {
+            res += `(${i}, ${j}), `;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const n = 5;
+let res;
+
+res = forLoop(n);
+console.log(`For loop sum result res = ${res}`);
+
+res = whileLoop(n);
+console.log(`While loop sum result res = ${res}`);
+
+res = whileLoopII(n);
+console.log(`While loop (two updates) sum result res = ${res}`);
+
+const resStr = nestedForLoop(n);
+console.log(`Nested for loop traversal result ${resStr}`);

en/codes/javascript/chapter_computational_complexity/recursion.js

@@ -0,0 +1,69 @@
+/**
+ * File: recursion.js
+ * Created Time: 2023-08-28
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Recursion */
+function recur(n) {
+    // Termination condition
+    if (n === 1) return 1;
+    // Recurse: recursive call
+    const res = recur(n - 1);
+    // Return: return result
+    return n + res;
+}
+
+/* Simulate recursion using iteration */
+function forLoopRecur(n) {
+    // Use an explicit stack to simulate the system call stack
+    const stack = [];
+    let res = 0;
+    // Recurse: recursive call
+    for (let i = n; i > 0; i--) {
+        // Simulate "recurse" with "push"
+        stack.push(i);
+    }
+    // Return: return result
+    while (stack.length) {
+        // Simulate "return" with "pop"
+        res += stack.pop();
+    }
+    // res = 1+2+3+...+n
+    return res;
+}
+
+/* Tail recursion */
+function tailRecur(n, res) {
+    // Termination condition
+    if (n === 0) return res;
+    // Tail recursive call
+    return tailRecur(n - 1, res + n);
+}
+
+/* Fibonacci sequence: recursion */
+function fib(n) {
+    // Termination condition f(1) = 0, f(2) = 1
+    if (n === 1 || n === 2) return n - 1;
+    // Recursive call f(n) = f(n-1) + f(n-2)
+    const res = fib(n - 1) + fib(n - 2);
+    // Return result f(n)
+    return res;
+}
+
+/* Driver Code */
+const n = 5;
+let res;
+
+res = recur(n);
+console.log(`Recursion sum result res = ${res}`);
+
+res = forLoopRecur(n);
+console.log(`Using iteration to simulate recursion sum result res = ${res}`);
+
+res = tailRecur(n, 0);
+console.log(`Tail recursion sum result res = ${res}`);
+
+res = fib(n);
+console.log(`The ${n}th Fibonacci number is ${res}`);
+

en/codes/javascript/chapter_computational_complexity/space_complexity.js

@@ -0,0 +1,103 @@
+/**
+ * File: space_complexity.js
+ * Created Time: 2023-02-05
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { ListNode } = require('../modules/ListNode');
+const { TreeNode } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Function */
+function constFunc() {
+    // Perform some operations
+    return 0;
+}
+
+/* Constant order */
+function constant(n) {
+    // Constants, variables, objects occupy O(1) space
+    const a = 0;
+    const b = 0;
+    const nums = new Array(10000);
+    const node = new ListNode(0);
+    // Variables in the loop occupy O(1) space
+    for (let i = 0; i < n; i++) {
+        const c = 0;
+    }
+    // Functions in the loop occupy O(1) space
+    for (let i = 0; i < n; i++) {
+        constFunc();
+    }
+}
+
+/* Linear order */
+function linear(n) {
+    // Array of length n uses O(n) space
+    const nums = new Array(n);
+    // A list of length n occupies O(n) space
+    const nodes = [];
+    for (let i = 0; i < n; i++) {
+        nodes.push(new ListNode(i));
+    }
+    // A hash table of length n occupies O(n) space
+    const map = new Map();
+    for (let i = 0; i < n; i++) {
+        map.set(i, i.toString());
+    }
+}
+
+/* Linear order (recursive implementation) */
+function linearRecur(n) {
+    console.log(`Recursion n = ${n}`);
+    if (n === 1) return;
+    linearRecur(n - 1);
+}
+
+/* Exponential order */
+function quadratic(n) {
+    // Matrix uses O(n^2) space
+    const numMatrix = Array(n)
+        .fill(null)
+        .map(() => Array(n).fill(null));
+    // 2D list uses O(n^2) space
+    const numList = [];
+    for (let i = 0; i < n; i++) {
+        const tmp = [];
+        for (let j = 0; j < n; j++) {
+            tmp.push(0);
+        }
+        numList.push(tmp);
+    }
+}
+
+/* Quadratic order (recursive implementation) */
+function quadraticRecur(n) {
+    if (n <= 0) return 0;
+    const nums = new Array(n);
+    console.log(`In recursion n = ${n}, nums length = ${nums.length}`);
+    return quadraticRecur(n - 1);
+}
+
+/* Driver Code */
+function buildTree(n) {
+    if (n === 0) return null;
+    const root = new TreeNode(0);
+    root.left = buildTree(n - 1);
+    root.right = buildTree(n - 1);
+    return root;
+}
+
+/* Driver Code */
+const n = 5;
+// Constant order
+constant(n);
+// Linear order
+linear(n);
+linearRecur(n);
+// Exponential order
+quadratic(n);
+quadraticRecur(n);
+// Exponential order
+const root = buildTree(n);
+printTree(root);

en/codes/javascript/chapter_computational_complexity/time_complexity.js

@@ -0,0 +1,155 @@
+/**
+ * File: time_complexity.js
+ * Created Time: 2023-01-02
+ * Author: RiverTwilight (contact@rene.wang)
+ */
+
+/* Constant order */
+function constant(n) {
+    let count = 0;
+    const size = 100000;
+    for (let i = 0; i < size; i++) count++;
+    return count;
+}
+
+/* Linear order */
+function linear(n) {
+    let count = 0;
+    for (let i = 0; i < n; i++) count++;
+    return count;
+}
+
+/* Linear order (traversing array) */
+function arrayTraversal(nums) {
+    let count = 0;
+    // Number of iterations is proportional to the array length
+    for (let i = 0; i < nums.length; i++) {
+        count++;
+    }
+    return count;
+}
+
+/* Exponential order */
+function quadratic(n) {
+    let count = 0;
+    // Number of iterations is quadratically related to the data size n
+    for (let i = 0; i < n; i++) {
+        for (let j = 0; j < n; j++) {
+            count++;
+        }
+    }
+    return count;
+}
+
+/* Quadratic order (bubble sort) */
+function bubbleSort(nums) {
+    let count = 0; // Counter
+    // Outer loop: unsorted range is [0, i]
+    for (let i = nums.length - 1; i > 0; i--) {
+        // Inner loop: swap the largest element in the unsorted range [0, i] to the rightmost end of that range
+        for (let j = 0; j < i; j++) {
+            if (nums[j] > nums[j + 1]) {
+                // Swap nums[j] and nums[j + 1]
+                let tmp = nums[j];
+                nums[j] = nums[j + 1];
+                nums[j + 1] = tmp;
+                count += 3; // Element swap includes 3 unit operations
+            }
+        }
+    }
+    return count;
+}
+
+/* Exponential order (loop implementation) */
+function exponential(n) {
+    let count = 0,
+        base = 1;
+    // Cells divide into two every round, forming sequence 1, 2, 4, 8, ..., 2^(n-1)
+    for (let i = 0; i < n; i++) {
+        for (let j = 0; j < base; j++) {
+            count++;
+        }
+        base *= 2;
+    }
+    // count = 1 + 2 + 4 + 8 + .. + 2^(n-1) = 2^n - 1
+    return count;
+}
+
+/* Exponential order (recursive implementation) */
+function expRecur(n) {
+    if (n === 1) return 1;
+    return expRecur(n - 1) + expRecur(n - 1) + 1;
+}
+
+/* Logarithmic order (loop implementation) */
+function logarithmic(n) {
+    let count = 0;
+    while (n > 1) {
+        n = n / 2;
+        count++;
+    }
+    return count;
+}
+
+/* Logarithmic order (recursive implementation) */
+function logRecur(n) {
+    if (n <= 1) return 0;
+    return logRecur(n / 2) + 1;
+}
+
+/* Linearithmic order */
+function linearLogRecur(n) {
+    if (n <= 1) return 1;
+    let count = linearLogRecur(n / 2) + linearLogRecur(n / 2);
+    for (let i = 0; i < n; i++) {
+        count++;
+    }
+    return count;
+}
+
+/* Factorial order (recursive implementation) */
+function factorialRecur(n) {
+    if (n === 0) return 1;
+    let count = 0;
+    // Split from 1 into n
+    for (let i = 0; i < n; i++) {
+        count += factorialRecur(n - 1);
+    }
+    return count;
+}
+
+/* Driver Code */
+// You can modify n to run and observe the trend of the number of operations for various complexities
+const n = 8;
+console.log('Input data size n = ' + n);
+
+let count = constant(n);
+console.log('Constant order operation count = ' + count);
+
+count = linear(n);
+console.log('Linear order operation count = ' + count);
+count = arrayTraversal(new Array(n));
+console.log('Linear order (array traversal) operation count = ' + count);
+
+count = quadratic(n);
+console.log('Quadratic order operation count = ' + count);
+let nums = new Array(n);
+for (let i = 0; i < n; i++) nums[i] = n - i; // [n,n-1,...,2,1]
+count = bubbleSort(nums);
+console.log('Quadratic order (bubble sort) operation count = ' + count);
+
+count = exponential(n);
+console.log('Exponential order (loop implementation) operation count = ' + count);
+count = expRecur(n);
+console.log('Exponential order (recursive implementation) operation count = ' + count);
+
+count = logarithmic(n);
+console.log('Logarithmic order (loop implementation) operation count = ' + count);
+count = logRecur(n);
+console.log('Logarithmic order (recursive implementation) operation count = ' + count);
+
+count = linearLogRecur(n);
+console.log('Linearithmic order (recursive implementation) operation count = ' + count);
+
+count = factorialRecur(n);
+console.log('Factorial order (recursive implementation) operation count = ' + count);

en/codes/javascript/chapter_computational_complexity/worst_best_time_complexity.js

@@ -0,0 +1,43 @@
+/**
+ * File: worst_best_time_complexity.js
+ * Created Time: 2023-01-05
+ * Author: RiverTwilight (contact@rene.wang)
+ */
+
+/* Generate an array with elements { 1, 2, ..., n }, order shuffled */
+function randomNumbers(n) {
+    const nums = Array(n);
+    // Generate array nums = { 1, 2, 3, ..., n }
+    for (let i = 0; i < n; i++) {
+        nums[i] = i + 1;
+    }
+    // Randomly shuffle array elements
+    for (let i = 0; i < n; i++) {
+        const r = Math.floor(Math.random() * (i + 1));
+        const temp = nums[i];
+        nums[i] = nums[r];
+        nums[r] = temp;
+    }
+    return nums;
+}
+
+/* Find the index of number 1 in array nums */
+function findOne(nums) {
+    for (let i = 0; i < nums.length; i++) {
+        // When element 1 is at the head of the array, best time complexity O(1) is achieved
+        // When element 1 is at the tail of the array, worst time complexity O(n) is achieved
+        if (nums[i] === 1) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+/* Driver Code */
+for (let i = 0; i < 10; i++) {
+    const n = 100;
+    const nums = randomNumbers(n);
+    const index = findOne(nums);
+    console.log('\nArray [ 1, 2, ..., n ] after shuffling = [' + nums.join(', ') + ']');
+    console.log('Index of number 1 is ' + index);
+}

en/codes/javascript/chapter_divide_and_conquer/binary_search_recur.js

@@ -0,0 +1,39 @@
+/**
+ * File: binary_search_recur.js
+ * Created Time: 2023-07-30
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Binary search: problem f(i, j) */
+function dfs(nums, target, i, j) {
+    // If the interval is empty, it means there is no target element, return -1
+    if (i > j) {
+        return -1;
+    }
+    // Calculate the midpoint index m
+    const m = i + ((j - i) >> 1);
+    if (nums[m] < target) {
+        // Recursion subproblem f(m+1, j)
+        return dfs(nums, target, m + 1, j);
+    } else if (nums[m] > target) {
+        // Recursion subproblem f(i, m-1)
+        return dfs(nums, target, i, m - 1);
+    } else {
+        // Found the target element, return its index
+        return m;
+    }
+}
+
+/* Binary search */
+function binarySearch(nums, target) {
+    const n = nums.length;
+    // Solve the problem f(0, n-1)
+    return dfs(nums, target, 0, n - 1);
+}
+
+/* Driver Code */
+const target = 6;
+const nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];
+// Binary search (closed interval on both sides)
+const index = binarySearch(nums, target);
+console.log(`Index of target element 6 is ${index}`);

en/codes/javascript/chapter_divide_and_conquer/build_tree.js

@@ -0,0 +1,44 @@
+/**
+ * File: build_tree.js
+ * Created Time: 2023-07-30
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+const { printTree } = require('../modules/PrintUtil');
+const { TreeNode } = require('../modules/TreeNode');
+
+/* Build binary tree: divide and conquer */
+function dfs(preorder, inorderMap, i, l, r) {
+    // Terminate when the subtree interval is empty
+    if (r - l < 0) return null;
+    // Initialize the root node
+    const root = new TreeNode(preorder[i]);
+    // Query m to divide the left and right subtrees
+    const m = inorderMap.get(preorder[i]);
+    // Subproblem: build the left subtree
+    root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
+    // Subproblem: build the right subtree
+    root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
+    // Return the root node
+    return root;
+}
+
+/* Build binary tree */
+function buildTree(preorder, inorder) {
+    // Initialize hash map, storing the mapping from inorder elements to indices
+    let inorderMap = new Map();
+    for (let i = 0; i < inorder.length; i++) {
+        inorderMap.set(inorder[i], i);
+    }
+    const root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
+    return root;
+}
+
+/* Driver Code */
+const preorder = [3, 9, 2, 1, 7];
+const inorder = [9, 3, 1, 2, 7];
+console.log('Preorder traversal = ' + JSON.stringify(preorder));
+console.log('Inorder traversal = ' + JSON.stringify(inorder));
+const root = buildTree(preorder, inorder);
+console.log('The constructed binary tree is:');
+printTree(root);

en/codes/javascript/chapter_divide_and_conquer/hanota.js

@@ -0,0 +1,52 @@
+/**
+ * File: hanota.js
+ * Created Time: 2023-07-30
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Move a disk */
+function move(src, tar) {
+    // Take out a disk from the top of src
+    const pan = src.pop();
+    // Place the disk on top of tar
+    tar.push(pan);
+}
+
+/* Solve the Tower of Hanoi problem f(i) */
+function dfs(i, src, buf, tar) {
+    // If there is only one disk left in src, move it directly to tar
+    if (i === 1) {
+        move(src, tar);
+        return;
+    }
+    // Subproblem f(i-1): move the top i-1 disks from src to buf using tar
+    dfs(i - 1, src, tar, buf);
+    // Subproblem f(1): move the remaining disk from src to tar
+    move(src, tar);
+    // Subproblem f(i-1): move the top i-1 disks from buf to tar using src
+    dfs(i - 1, buf, src, tar);
+}
+
+/* Solve the Tower of Hanoi problem */
+function solveHanota(A, B, C) {
+    const n = A.length;
+    // Move the top n disks from A to C using B
+    dfs(n, A, B, C);
+}
+
+/* Driver Code */
+// The tail of the list is the top of the rod
+const A = [5, 4, 3, 2, 1];
+const B = [];
+const C = [];
+console.log('In initial state:');
+console.log(`A = ${JSON.stringify(A)}`);
+console.log(`B = ${JSON.stringify(B)}`);
+console.log(`C = ${JSON.stringify(C)}`);
+
+solveHanota(A, B, C);
+
+console.log('After disk movement is complete:');
+console.log(`A = ${JSON.stringify(A)}`);
+console.log(`B = ${JSON.stringify(B)}`);
+console.log(`C = ${JSON.stringify(C)}`);

en/codes/javascript/chapter_dynamic_programming/climbing_stairs_backtrack.js

@@ -0,0 +1,34 @@
+/**
+ * File: climbing_stairs_backtrack.js
+ * Created Time: 2023-07-26
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Backtracking */
+function backtrack(choices, state, n, res) {
+    // When climbing to the n-th stair, add 1 to the solution count
+    if (state === n) res.set(0, res.get(0) + 1);
+    // Traverse all choices
+    for (const choice of choices) {
+        // Pruning: not allowed to go beyond the n-th stair
+        if (state + choice > n) continue;
+        // Attempt: make choice, update state
+        backtrack(choices, state + choice, n, res);
+        // Backtrack
+    }
+}
+
+/* Climbing stairs: Backtracking */
+function climbingStairsBacktrack(n) {
+    const choices = [1, 2]; // Can choose to climb up 1 or 2 stairs
+    const state = 0; // Start climbing from the 0-th stair
+    const res = new Map();
+    res.set(0, 0); // Use res[0] to record the solution count
+    backtrack(choices, state, n, res);
+    return res.get(0);
+}
+
+/* Driver Code */
+const n = 9;
+const res = climbingStairsBacktrack(n);
+console.log(`Climbing ${n} stairs has ${res} solutions`);

en/codes/javascript/chapter_dynamic_programming/climbing_stairs_constraint_dp.js

@@ -0,0 +1,30 @@
+/**
+ * File: climbing_stairs_constraint_dp.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Climbing stairs with constraint: Dynamic programming */
+function climbingStairsConstraintDP(n) {
+    if (n === 1 || n === 2) {
+        return 1;
+    }
+    // Initialize dp table, used to store solutions to subproblems
+    const dp = Array.from(new Array(n + 1), () => new Array(3));
+    // Initial state: preset the solution to the smallest subproblem
+    dp[1][1] = 1;
+    dp[1][2] = 0;
+    dp[2][1] = 0;
+    dp[2][2] = 1;
+    // State transition: gradually solve larger subproblems from smaller ones
+    for (let i = 3; i <= n; i++) {
+        dp[i][1] = dp[i - 1][2];
+        dp[i][2] = dp[i - 2][1] + dp[i - 2][2];
+    }
+    return dp[n][1] + dp[n][2];
+}
+
+/* Driver Code */
+const n = 9;
+const res = climbingStairsConstraintDP(n);
+console.log(`Climbing ${n} stairs has ${res} solutions`);

en/codes/javascript/chapter_dynamic_programming/climbing_stairs_dfs.js

@@ -0,0 +1,24 @@
+/**
+ * File: climbing_stairs_dfs.js
+ * Created Time: 2023-07-26
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Search */
+function dfs(i) {
+    // Known dp[1] and dp[2], return them
+    if (i === 1 || i === 2) return i;
+    // dp[i] = dp[i-1] + dp[i-2]
+    const count = dfs(i - 1) + dfs(i - 2);
+    return count;
+}
+
+/* Climbing stairs: Search */
+function climbingStairsDFS(n) {
+    return dfs(n);
+}
+
+/* Driver Code */
+const n = 9;
+const res = climbingStairsDFS(n);
+console.log(`Climbing ${n} stairs has ${res} solutions`);

en/codes/javascript/chapter_dynamic_programming/climbing_stairs_dfs_mem.js

@@ -0,0 +1,30 @@
+/**
+ * File: climbing_stairs_dfs_mem.js
+ * Created Time: 2023-07-26
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Memoization search */
+function dfs(i, mem) {
+    // Known dp[1] and dp[2], return them
+    if (i === 1 || i === 2) return i;
+    // If record dp[i] exists, return it directly
+    if (mem[i] != -1) return mem[i];
+    // dp[i] = dp[i-1] + dp[i-2]
+    const count = dfs(i - 1, mem) + dfs(i - 2, mem);
+    // Record dp[i]
+    mem[i] = count;
+    return count;
+}
+
+/* Climbing stairs: Memoization search */
+function climbingStairsDFSMem(n) {
+    // mem[i] records the total number of solutions to climb to the i-th stair, -1 means no record
+    const mem = new Array(n + 1).fill(-1);
+    return dfs(n, mem);
+}
+
+/* Driver Code */
+const n = 9;
+const res = climbingStairsDFSMem(n);
+console.log(`Climbing ${n} stairs has ${res} solutions`);

en/codes/javascript/chapter_dynamic_programming/climbing_stairs_dp.js

@@ -0,0 +1,40 @@
+/**
+ * File: climbing_stairs_dp.js
+ * Created Time: 2023-07-26
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Climbing stairs: Dynamic programming */
+function climbingStairsDP(n) {
+    if (n === 1 || n === 2) return n;
+    // Initialize dp table, used to store solutions to subproblems
+    const dp = new Array(n + 1).fill(-1);
+    // Initial state: preset the solution to the smallest subproblem
+    dp[1] = 1;
+    dp[2] = 2;
+    // State transition: gradually solve larger subproblems from smaller ones
+    for (let i = 3; i <= n; i++) {
+        dp[i] = dp[i - 1] + dp[i - 2];
+    }
+    return dp[n];
+}
+
+/* Climbing stairs: Space-optimized dynamic programming */
+function climbingStairsDPComp(n) {
+    if (n === 1 || n === 2) return n;
+    let a = 1,
+        b = 2;
+    for (let i = 3; i <= n; i++) {
+        const tmp = b;
+        b = a + b;
+        a = tmp;
+    }
+    return b;
+}
+
+/* Driver Code */
+const n = 9;
+let res = climbingStairsDP(n);
+console.log(`Climbing ${n} stairs has ${res} solutions`);
+res = climbingStairsDPComp(n);
+console.log(`Climbing ${n} stairs has ${res} solutions`);

en/codes/javascript/chapter_dynamic_programming/coin_change.js

@@ -0,0 +1,66 @@
+/**
+ * File: coin_change.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Coin change: Dynamic programming */
+function coinChangeDP(coins, amt) {
+    const n = coins.length;
+    const MAX = amt + 1;
+    // Initialize dp table
+    const dp = Array.from({ length: n + 1 }, () =>
+        Array.from({ length: amt + 1 }, () => 0)
+    );
+    // State transition: first row and first column
+    for (let a = 1; a <= amt; a++) {
+        dp[0][a] = MAX;
+    }
+    // State transition: rest of the rows and columns
+    for (let i = 1; i <= n; i++) {
+        for (let a = 1; a <= amt; a++) {
+            if (coins[i - 1] > a) {
+                // If exceeds target amount, don't select coin i
+                dp[i][a] = dp[i - 1][a];
+            } else {
+                // The smaller value between not selecting and selecting coin i
+                dp[i][a] = Math.min(dp[i - 1][a], dp[i][a - coins[i - 1]] + 1);
+            }
+        }
+    }
+    return dp[n][amt] !== MAX ? dp[n][amt] : -1;
+}
+
+/* Coin change: Space-optimized dynamic programming */
+function coinChangeDPComp(coins, amt) {
+    const n = coins.length;
+    const MAX = amt + 1;
+    // Initialize dp table
+    const dp = Array.from({ length: amt + 1 }, () => MAX);
+    dp[0] = 0;
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        for (let a = 1; a <= amt; a++) {
+            if (coins[i - 1] > a) {
+                // If exceeds target amount, don't select coin i
+                dp[a] = dp[a];
+            } else {
+                // The smaller value between not selecting and selecting coin i
+                dp[a] = Math.min(dp[a], dp[a - coins[i - 1]] + 1);
+            }
+        }
+    }
+    return dp[amt] !== MAX ? dp[amt] : -1;
+}
+
+/* Driver Code */
+const coins = [1, 2, 5];
+const amt = 4;
+
+// Dynamic programming
+let res = coinChangeDP(coins, amt);
+console.log(`Minimum coins needed to make target amount is ${res}`);
+
+// Space-optimized dynamic programming
+res = coinChangeDPComp(coins, amt);
+console.log(`Minimum coins needed to make target amount is ${res}`);

en/codes/javascript/chapter_dynamic_programming/coin_change_ii.js

@@ -0,0 +1,64 @@
+/**
+ * File: coin_change_ii.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Coin change II: Dynamic programming */
+function coinChangeIIDP(coins, amt) {
+    const n = coins.length;
+    // Initialize dp table
+    const dp = Array.from({ length: n + 1 }, () =>
+        Array.from({ length: amt + 1 }, () => 0)
+    );
+    // Initialize first column
+    for (let i = 0; i <= n; i++) {
+        dp[i][0] = 1;
+    }
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        for (let a = 1; a <= amt; a++) {
+            if (coins[i - 1] > a) {
+                // If exceeds target amount, don't select coin i
+                dp[i][a] = dp[i - 1][a];
+            } else {
+                // Sum of the two options: not selecting and selecting coin i
+                dp[i][a] = dp[i - 1][a] + dp[i][a - coins[i - 1]];
+            }
+        }
+    }
+    return dp[n][amt];
+}
+
+/* Coin change II: Space-optimized dynamic programming */
+function coinChangeIIDPComp(coins, amt) {
+    const n = coins.length;
+    // Initialize dp table
+    const dp = Array.from({ length: amt + 1 }, () => 0);
+    dp[0] = 1;
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        for (let a = 1; a <= amt; a++) {
+            if (coins[i - 1] > a) {
+                // If exceeds target amount, don't select coin i
+                dp[a] = dp[a];
+            } else {
+                // Sum of the two options: not selecting and selecting coin i
+                dp[a] = dp[a] + dp[a - coins[i - 1]];
+            }
+        }
+    }
+    return dp[amt];
+}
+
+/* Driver Code */
+const coins = [1, 2, 5];
+const amt = 5;
+
+// Dynamic programming
+let res = coinChangeIIDP(coins, amt);
+console.log(`Number of coin combinations to make target amount is ${res}`);
+
+// Space-optimized dynamic programming
+res = coinChangeIIDPComp(coins, amt);
+console.log(`Number of coin combinations to make target amount is ${res}`);

en/codes/javascript/chapter_dynamic_programming/edit_distance.js

@@ -0,0 +1,135 @@
+/**
+ * File: edit_distance.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Edit distance: Brute-force search */
+function editDistanceDFS(s, t, i, j) {
+    // If both s and t are empty, return 0
+    if (i === 0 && j === 0) return 0;
+
+    // If s is empty, return length of t
+    if (i === 0) return j;
+
+    // If t is empty, return length of s
+    if (j === 0) return i;
+
+    // If two characters are equal, skip both characters
+    if (s.charAt(i - 1) === t.charAt(j - 1))
+        return editDistanceDFS(s, t, i - 1, j - 1);
+
+    // Minimum edit steps = minimum edit steps of insert, delete, replace + 1
+    const insert = editDistanceDFS(s, t, i, j - 1);
+    const del = editDistanceDFS(s, t, i - 1, j);
+    const replace = editDistanceDFS(s, t, i - 1, j - 1);
+    // Return minimum edit steps
+    return Math.min(insert, del, replace) + 1;
+}
+
+/* Edit distance: Memoization search */
+function editDistanceDFSMem(s, t, mem, i, j) {
+    // If both s and t are empty, return 0
+    if (i === 0 && j === 0) return 0;
+
+    // If s is empty, return length of t
+    if (i === 0) return j;
+
+    // If t is empty, return length of s
+    if (j === 0) return i;
+
+    // If there's a record, return it directly
+    if (mem[i][j] !== -1) return mem[i][j];
+
+    // If two characters are equal, skip both characters
+    if (s.charAt(i - 1) === t.charAt(j - 1))
+        return editDistanceDFSMem(s, t, mem, i - 1, j - 1);
+
+    // Minimum edit steps = minimum edit steps of insert, delete, replace + 1
+    const insert = editDistanceDFSMem(s, t, mem, i, j - 1);
+    const del = editDistanceDFSMem(s, t, mem, i - 1, j);
+    const replace = editDistanceDFSMem(s, t, mem, i - 1, j - 1);
+    // Record and return minimum edit steps
+    mem[i][j] = Math.min(insert, del, replace) + 1;
+    return mem[i][j];
+}
+
+/* Edit distance: Dynamic programming */
+function editDistanceDP(s, t) {
+    const n = s.length,
+        m = t.length;
+    const dp = Array.from({ length: n + 1 }, () => new Array(m + 1).fill(0));
+    // State transition: first row and first column
+    for (let i = 1; i <= n; i++) {
+        dp[i][0] = i;
+    }
+    for (let j = 1; j <= m; j++) {
+        dp[0][j] = j;
+    }
+    // State transition: rest of the rows and columns
+    for (let i = 1; i <= n; i++) {
+        for (let j = 1; j <= m; j++) {
+            if (s.charAt(i - 1) === t.charAt(j - 1)) {
+                // If two characters are equal, skip both characters
+                dp[i][j] = dp[i - 1][j - 1];
+            } else {
+                // Minimum edit steps = minimum edit steps of insert, delete, replace + 1
+                dp[i][j] =
+                    Math.min(dp[i][j - 1], dp[i - 1][j], dp[i - 1][j - 1]) + 1;
+            }
+        }
+    }
+    return dp[n][m];
+}
+
+/* Edit distance: Space-optimized dynamic programming */
+function editDistanceDPComp(s, t) {
+    const n = s.length,
+        m = t.length;
+    const dp = new Array(m + 1).fill(0);
+    // State transition: first row
+    for (let j = 1; j <= m; j++) {
+        dp[j] = j;
+    }
+    // State transition: rest of the rows
+    for (let i = 1; i <= n; i++) {
+        // State transition: first column
+        let leftup = dp[0]; // Temporarily store dp[i-1, j-1]
+        dp[0] = i;
+        // State transition: rest of the columns
+        for (let j = 1; j <= m; j++) {
+            const temp = dp[j];
+            if (s.charAt(i - 1) === t.charAt(j - 1)) {
+                // If two characters are equal, skip both characters
+                dp[j] = leftup;
+            } else {
+                // Minimum edit steps = minimum edit steps of insert, delete, replace + 1
+                dp[j] = Math.min(dp[j - 1], dp[j], leftup) + 1;
+            }
+            leftup = temp; // Update for next round's dp[i-1, j-1]
+        }
+    }
+    return dp[m];
+}
+
+const s = 'bag';
+const t = 'pack';
+const n = s.length,
+    m = t.length;
+
+// Brute-force search
+let res = editDistanceDFS(s, t, n, m);
+console.log(`Changing ${s} to ${t} requires minimum ${res} edits`);
+
+// Memoization search
+const mem = Array.from(new Array(n + 1), () => new Array(m + 1).fill(-1));
+res = editDistanceDFSMem(s, t, mem, n, m);
+console.log(`Changing ${s} to ${t} requires minimum ${res} edits`);
+
+// Dynamic programming
+res = editDistanceDP(s, t);
+console.log(`Changing ${s} to ${t} requires minimum ${res} edits`);
+
+// Space-optimized dynamic programming
+res = editDistanceDPComp(s, t);
+console.log(`Changing ${s} to ${t} requires minimum ${res} edits`);

en/codes/javascript/chapter_dynamic_programming/knapsack.js

@@ -0,0 +1,113 @@
+/**
+ * File: knapsack.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* 0-1 knapsack: Brute-force search */
+function knapsackDFS(wgt, val, i, c) {
+    // If all items have been selected or knapsack has no remaining capacity, return value 0
+    if (i === 0 || c === 0) {
+        return 0;
+    }
+    // If exceeds knapsack capacity, can only choose not to put it in
+    if (wgt[i - 1] > c) {
+        return knapsackDFS(wgt, val, i - 1, c);
+    }
+    // Calculate the maximum value of not putting in and putting in item i
+    const no = knapsackDFS(wgt, val, i - 1, c);
+    const yes = knapsackDFS(wgt, val, i - 1, c - wgt[i - 1]) + val[i - 1];
+    // Return the larger value of the two options
+    return Math.max(no, yes);
+}
+
+/* 0-1 knapsack: Memoization search */
+function knapsackDFSMem(wgt, val, mem, i, c) {
+    // If all items have been selected or knapsack has no remaining capacity, return value 0
+    if (i === 0 || c === 0) {
+        return 0;
+    }
+    // If there's a record, return it directly
+    if (mem[i][c] !== -1) {
+        return mem[i][c];
+    }
+    // If exceeds knapsack capacity, can only choose not to put it in
+    if (wgt[i - 1] > c) {
+        return knapsackDFSMem(wgt, val, mem, i - 1, c);
+    }
+    // Calculate the maximum value of not putting in and putting in item i
+    const no = knapsackDFSMem(wgt, val, mem, i - 1, c);
+    const yes =
+        knapsackDFSMem(wgt, val, mem, i - 1, c - wgt[i - 1]) + val[i - 1];
+    // Record and return the larger value of the two options
+    mem[i][c] = Math.max(no, yes);
+    return mem[i][c];
+}
+
+/* 0-1 knapsack: Dynamic programming */
+function knapsackDP(wgt, val, cap) {
+    const n = wgt.length;
+    // Initialize dp table
+    const dp = Array(n + 1)
+        .fill(0)
+        .map(() => Array(cap + 1).fill(0));
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        for (let c = 1; c <= cap; c++) {
+            if (wgt[i - 1] > c) {
+                // If exceeds knapsack capacity, don't select item i
+                dp[i][c] = dp[i - 1][c];
+            } else {
+                // The larger value between not selecting and selecting item i
+                dp[i][c] = Math.max(
+                    dp[i - 1][c],
+                    dp[i - 1][c - wgt[i - 1]] + val[i - 1]
+                );
+            }
+        }
+    }
+    return dp[n][cap];
+}
+
+/* 0-1 knapsack: Space-optimized dynamic programming */
+function knapsackDPComp(wgt, val, cap) {
+    const n = wgt.length;
+    // Initialize dp table
+    const dp = Array(cap + 1).fill(0);
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        // Traverse in reverse order
+        for (let c = cap; c >= 1; c--) {
+            if (wgt[i - 1] <= c) {
+                // The larger value between not selecting and selecting item i
+                dp[c] = Math.max(dp[c], dp[c - wgt[i - 1]] + val[i - 1]);
+            }
+        }
+    }
+    return dp[cap];
+}
+
+/* Driver Code */
+const wgt = [10, 20, 30, 40, 50];
+const val = [50, 120, 150, 210, 240];
+const cap = 50;
+const n = wgt.length;
+
+// Brute-force search
+let res = knapsackDFS(wgt, val, n, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);
+
+// Memoization search
+const mem = Array.from({ length: n + 1 }, () =>
+    Array.from({ length: cap + 1 }, () => -1)
+);
+res = knapsackDFSMem(wgt, val, mem, n, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);
+
+// Dynamic programming
+res = knapsackDP(wgt, val, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);
+
+// Space-optimized dynamic programming
+res = knapsackDPComp(wgt, val, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);

en/codes/javascript/chapter_dynamic_programming/min_cost_climbing_stairs_dp.js

@@ -0,0 +1,49 @@
+/**
+ * File: min_cost_climbing_stairs_dp.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Minimum cost climbing stairs: Dynamic programming */
+function minCostClimbingStairsDP(cost) {
+    const n = cost.length - 1;
+    if (n === 1 || n === 2) {
+        return cost[n];
+    }
+    // Initialize dp table, used to store solutions to subproblems
+    const dp = new Array(n + 1);
+    // Initial state: preset the solution to the smallest subproblem
+    dp[1] = cost[1];
+    dp[2] = cost[2];
+    // State transition: gradually solve larger subproblems from smaller ones
+    for (let i = 3; i <= n; i++) {
+        dp[i] = Math.min(dp[i - 1], dp[i - 2]) + cost[i];
+    }
+    return dp[n];
+}
+
+/* Minimum cost climbing stairs: Space-optimized dynamic programming */
+function minCostClimbingStairsDPComp(cost) {
+    const n = cost.length - 1;
+    if (n === 1 || n === 2) {
+        return cost[n];
+    }
+    let a = cost[1],
+        b = cost[2];
+    for (let i = 3; i <= n; i++) {
+        const tmp = b;
+        b = Math.min(a, tmp) + cost[i];
+        a = tmp;
+    }
+    return b;
+}
+
+/* Driver Code */
+const cost = [0, 1, 10, 1, 1, 1, 10, 1, 1, 10, 1];
+console.log('Input stair cost list is:', cost);
+
+let res = minCostClimbingStairsDP(cost);
+console.log(`Minimum cost to climb stairs is: ${res}`);
+
+res = minCostClimbingStairsDPComp(cost);
+console.log(`Minimum cost to climb stairs is: ${res}`);

en/codes/javascript/chapter_dynamic_programming/min_path_sum.js

@@ -0,0 +1,121 @@
+/**
+ * File: min_path_sum.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Minimum path sum: Brute-force search */
+function minPathSumDFS(grid, i, j) {
+    // If it's the top-left cell, terminate the search
+    if (i === 0 && j === 0) {
+        return grid[0][0];
+    }
+    // If row or column index is out of bounds, return +∞ cost
+    if (i < 0 || j < 0) {
+        return Infinity;
+    }
+    // Calculate the minimum path cost from top-left to (i-1, j) and (i, j-1)
+    const up = minPathSumDFS(grid, i - 1, j);
+    const left = minPathSumDFS(grid, i, j - 1);
+    // Return the minimum path cost from top-left to (i, j)
+    return Math.min(left, up) + grid[i][j];
+}
+
+/* Minimum path sum: Memoization search */
+function minPathSumDFSMem(grid, mem, i, j) {
+    // If it's the top-left cell, terminate the search
+    if (i === 0 && j === 0) {
+        return grid[0][0];
+    }
+    // If row or column index is out of bounds, return +∞ cost
+    if (i < 0 || j < 0) {
+        return Infinity;
+    }
+    // If there's a record, return it directly
+    if (mem[i][j] !== -1) {
+        return mem[i][j];
+    }
+    // Minimum path cost for left and upper cells
+    const up = minPathSumDFSMem(grid, mem, i - 1, j);
+    const left = minPathSumDFSMem(grid, mem, i, j - 1);
+    // Record and return the minimum path cost from top-left to (i, j)
+    mem[i][j] = Math.min(left, up) + grid[i][j];
+    return mem[i][j];
+}
+
+/* Minimum path sum: Dynamic programming */
+function minPathSumDP(grid) {
+    const n = grid.length,
+        m = grid[0].length;
+    // Initialize dp table
+    const dp = Array.from({ length: n }, () =>
+        Array.from({ length: m }, () => 0)
+    );
+    dp[0][0] = grid[0][0];
+    // State transition: first row
+    for (let j = 1; j < m; j++) {
+        dp[0][j] = dp[0][j - 1] + grid[0][j];
+    }
+    // State transition: first column
+    for (let i = 1; i < n; i++) {
+        dp[i][0] = dp[i - 1][0] + grid[i][0];
+    }
+    // State transition: rest of the rows and columns
+    for (let i = 1; i < n; i++) {
+        for (let j = 1; j < m; j++) {
+            dp[i][j] = Math.min(dp[i][j - 1], dp[i - 1][j]) + grid[i][j];
+        }
+    }
+    return dp[n - 1][m - 1];
+}
+
+/* Minimum path sum: Space-optimized dynamic programming */
+function minPathSumDPComp(grid) {
+    const n = grid.length,
+        m = grid[0].length;
+    // Initialize dp table
+    const dp = new Array(m);
+    // State transition: first row
+    dp[0] = grid[0][0];
+    for (let j = 1; j < m; j++) {
+        dp[j] = dp[j - 1] + grid[0][j];
+    }
+    // State transition: rest of the rows
+    for (let i = 1; i < n; i++) {
+        // State transition: first column
+        dp[0] = dp[0] + grid[i][0];
+        // State transition: rest of the columns
+        for (let j = 1; j < m; j++) {
+            dp[j] = Math.min(dp[j - 1], dp[j]) + grid[i][j];
+        }
+    }
+    return dp[m - 1];
+}
+
+/* Driver Code */
+const grid = [
+    [1, 3, 1, 5],
+    [2, 2, 4, 2],
+    [5, 3, 2, 1],
+    [4, 3, 5, 2],
+];
+const n = grid.length,
+    m = grid[0].length;
+// Brute-force search
+let res = minPathSumDFS(grid, n - 1, m - 1);
+console.log(`Minimum path sum from top-left to bottom-right is ${res}`);
+
+// Memoization search
+const mem = Array.from({ length: n }, () =>
+    Array.from({ length: m }, () => -1)
+);
+res = minPathSumDFSMem(grid, mem, n - 1, m - 1);
+console.log(`Minimum path sum from top-left to bottom-right is ${res}`);
+
+// Dynamic programming
+res = minPathSumDP(grid);
+console.log(`Minimum path sum from top-left to bottom-right is ${res}`);
+
+// Space-optimized dynamic programming
+res = minPathSumDPComp(grid);
+console.log(`Minimum path sum from top-left to bottom-right is ${res}`);

en/codes/javascript/chapter_dynamic_programming/unbounded_knapsack.js

@@ -0,0 +1,63 @@
+/**
+ * File: unbounded_knapsack.js
+ * Created Time: 2023-08-23
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Unbounded knapsack: Dynamic programming */
+function unboundedKnapsackDP(wgt, val, cap) {
+    const n = wgt.length;
+    // Initialize dp table
+    const dp = Array.from({ length: n + 1 }, () =>
+        Array.from({ length: cap + 1 }, () => 0)
+    );
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        for (let c = 1; c <= cap; c++) {
+            if (wgt[i - 1] > c) {
+                // If exceeds knapsack capacity, don't select item i
+                dp[i][c] = dp[i - 1][c];
+            } else {
+                // The larger value between not selecting and selecting item i
+                dp[i][c] = Math.max(
+                    dp[i - 1][c],
+                    dp[i][c - wgt[i - 1]] + val[i - 1]
+                );
+            }
+        }
+    }
+    return dp[n][cap];
+}
+
+/* Unbounded knapsack: Space-optimized dynamic programming */
+function unboundedKnapsackDPComp(wgt, val, cap) {
+    const n = wgt.length;
+    // Initialize dp table
+    const dp = Array.from({ length: cap + 1 }, () => 0);
+    // State transition
+    for (let i = 1; i <= n; i++) {
+        for (let c = 1; c <= cap; c++) {
+            if (wgt[i - 1] > c) {
+                // If exceeds knapsack capacity, don't select item i
+                dp[c] = dp[c];
+            } else {
+                // The larger value between not selecting and selecting item i
+                dp[c] = Math.max(dp[c], dp[c - wgt[i - 1]] + val[i - 1]);
+            }
+        }
+    }
+    return dp[cap];
+}
+
+/* Driver Code */
+const wgt = [1, 2, 3];
+const val = [5, 11, 15];
+const cap = 4;
+
+// Dynamic programming
+let res = unboundedKnapsackDP(wgt, val, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);
+
+// Space-optimized dynamic programming
+res = unboundedKnapsackDPComp(wgt, val, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);

en/codes/javascript/chapter_graph/graph_adjacency_list.js

@@ -0,0 +1,142 @@
+/**
+ * File: graph_adjacency_list.js
+ * Created Time: 2023-02-09
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { Vertex } = require('../modules/Vertex');
+
+/* Undirected graph class based on adjacency list */
+class GraphAdjList {
+    // Adjacency list, key: vertex, value: all adjacent vertices of that vertex
+    adjList;
+
+    /* Constructor */
+    constructor(edges) {
+        this.adjList = new Map();
+        // Add all vertices and edges
+        for (const edge of edges) {
+            this.addVertex(edge[0]);
+            this.addVertex(edge[1]);
+            this.addEdge(edge[0], edge[1]);
+        }
+    }
+
+    /* Get the number of vertices */
+    size() {
+        return this.adjList.size;
+    }
+
+    /* Add edge */
+    addEdge(vet1, vet2) {
+        if (
+            !this.adjList.has(vet1) ||
+            !this.adjList.has(vet2) ||
+            vet1 === vet2
+        ) {
+            throw new Error('Illegal Argument Exception');
+        }
+        // Add edge vet1 - vet2
+        this.adjList.get(vet1).push(vet2);
+        this.adjList.get(vet2).push(vet1);
+    }
+
+    /* Remove edge */
+    removeEdge(vet1, vet2) {
+        if (
+            !this.adjList.has(vet1) ||
+            !this.adjList.has(vet2) ||
+            vet1 === vet2 ||
+            this.adjList.get(vet1).indexOf(vet2) === -1
+        ) {
+            throw new Error('Illegal Argument Exception');
+        }
+        // Remove edge vet1 - vet2
+        this.adjList.get(vet1).splice(this.adjList.get(vet1).indexOf(vet2), 1);
+        this.adjList.get(vet2).splice(this.adjList.get(vet2).indexOf(vet1), 1);
+    }
+
+    /* Add vertex */
+    addVertex(vet) {
+        if (this.adjList.has(vet)) return;
+        // Add a new linked list in the adjacency list
+        this.adjList.set(vet, []);
+    }
+
+    /* Remove vertex */
+    removeVertex(vet) {
+        if (!this.adjList.has(vet)) {
+            throw new Error('Illegal Argument Exception');
+        }
+        // Remove the linked list corresponding to vertex vet in the adjacency list
+        this.adjList.delete(vet);
+        // Traverse the linked lists of other vertices and remove all edges containing vet
+        for (const set of this.adjList.values()) {
+            const index = set.indexOf(vet);
+            if (index > -1) {
+                set.splice(index, 1);
+            }
+        }
+    }
+
+    /* Print adjacency list */
+    print() {
+        console.log('Adjacency list =');
+        for (const [key, value] of this.adjList) {
+            const tmp = [];
+            for (const vertex of value) {
+                tmp.push(vertex.val);
+            }
+            console.log(key.val + ': ' + tmp.join());
+        }
+    }
+}
+
+if (require.main === module) {
+    /* Driver Code */
+    /* Add edge */
+    const v0 = new Vertex(1),
+        v1 = new Vertex(3),
+        v2 = new Vertex(2),
+        v3 = new Vertex(5),
+        v4 = new Vertex(4);
+    const edges = [
+        [v0, v1],
+        [v1, v2],
+        [v2, v3],
+        [v0, v3],
+        [v2, v4],
+        [v3, v4],
+    ];
+    const graph = new GraphAdjList(edges);
+    console.log('\nAfter initialization, graph is');
+    graph.print();
+
+    /* Add edge */
+    // Vertices 1, 2 are v0, v2
+    graph.addEdge(v0, v2);
+    console.log('\nAfter adding edge 1-2, graph is');
+    graph.print();
+
+    /* Remove edge */
+    // Vertices 1, 3 are v0, v1
+    graph.removeEdge(v0, v1);
+    console.log('\nAfter removing edge 1-3, graph is');
+    graph.print();
+
+    /* Add vertex */
+    const v5 = new Vertex(6);
+    graph.addVertex(v5);
+    console.log('\nAfter adding vertex 6, graph is');
+    graph.print();
+
+    /* Remove vertex */
+    // Vertex 3 is v1
+    graph.removeVertex(v1);
+    console.log('\nAfter removing vertex 3, graph is');
+    graph.print();
+}
+
+module.exports = {
+    GraphAdjList,
+};

en/codes/javascript/chapter_graph/graph_adjacency_matrix.js

@@ -0,0 +1,132 @@
+/**
+ * File: graph_adjacency_matrix.js
+ * Created Time: 2023-02-09
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+/* Undirected graph class based on adjacency matrix */
+class GraphAdjMat {
+    vertices; // Vertex list, where the element represents the "vertex value" and the index represents the "vertex index"
+    adjMat; // Adjacency matrix, where the row and column indices correspond to the "vertex index"
+
+    /* Constructor */
+    constructor(vertices, edges) {
+        this.vertices = [];
+        this.adjMat = [];
+        // Add vertex
+        for (const val of vertices) {
+            this.addVertex(val);
+        }
+        // Add edge
+        // Note that the edges elements represent vertex indices, i.e., corresponding to the vertices element indices
+        for (const e of edges) {
+            this.addEdge(e[0], e[1]);
+        }
+    }
+
+    /* Get the number of vertices */
+    size() {
+        return this.vertices.length;
+    }
+
+    /* Add vertex */
+    addVertex(val) {
+        const n = this.size();
+        // Add the value of the new vertex to the vertex list
+        this.vertices.push(val);
+        // Add a row to the adjacency matrix
+        const newRow = [];
+        for (let j = 0; j < n; j++) {
+            newRow.push(0);
+        }
+        this.adjMat.push(newRow);
+        // Add a column to the adjacency matrix
+        for (const row of this.adjMat) {
+            row.push(0);
+        }
+    }
+
+    /* Remove vertex */
+    removeVertex(index) {
+        if (index >= this.size()) {
+            throw new RangeError('Index Out Of Bounds Exception');
+        }
+        // Remove the vertex at index from the vertex list
+        this.vertices.splice(index, 1);
+
+        // Remove the row at index from the adjacency matrix
+        this.adjMat.splice(index, 1);
+        // Remove the column at index from the adjacency matrix
+        for (const row of this.adjMat) {
+            row.splice(index, 1);
+        }
+    }
+
+    /* Add edge */
+    // Parameters i, j correspond to the vertices element indices
+    addEdge(i, j) {
+        // Handle index out of bounds and equality
+        if (i < 0 || j < 0 || i >= this.size() || j >= this.size() || i === j) {
+            throw new RangeError('Index Out Of Bounds Exception');
+        }
+        // In undirected graph, adjacency matrix is symmetric about main diagonal, i.e., satisfies (i, j) === (j, i)
+        this.adjMat[i][j] = 1;
+        this.adjMat[j][i] = 1;
+    }
+
+    /* Remove edge */
+    // Parameters i, j correspond to the vertices element indices
+    removeEdge(i, j) {
+        // Handle index out of bounds and equality
+        if (i < 0 || j < 0 || i >= this.size() || j >= this.size() || i === j) {
+            throw new RangeError('Index Out Of Bounds Exception');
+        }
+        this.adjMat[i][j] = 0;
+        this.adjMat[j][i] = 0;
+    }
+
+    /* Print adjacency matrix */
+    print() {
+        console.log('Vertex list = ', this.vertices);
+        console.log('Adjacency matrix =', this.adjMat);
+    }
+}
+
+/* Driver Code */
+/* Add edge */
+// Note that the edges elements represent vertex indices, i.e., corresponding to the vertices element indices
+const vertices = [1, 3, 2, 5, 4];
+const edges = [
+    [0, 1],
+    [1, 2],
+    [2, 3],
+    [0, 3],
+    [2, 4],
+    [3, 4],
+];
+const graph = new GraphAdjMat(vertices, edges);
+console.log('\nAfter initialization, graph is');
+graph.print();
+
+/* Add edge */
+// Add vertex
+graph.addEdge(0, 2);
+console.log('\nAfter adding edge 1-2, graph is');
+graph.print();
+
+/* Remove edge */
+// Vertices 1, 3 have indices 0, 1 respectively
+graph.removeEdge(0, 1);
+console.log('\nAfter removing edge 1-3, graph is');
+graph.print();
+
+/* Add vertex */
+graph.addVertex(6);
+console.log('\nAfter adding vertex 6, graph is');
+graph.print();
+
+/* Remove vertex */
+// Vertex 3 has index 1
+graph.removeVertex(1);
+console.log('\nAfter removing vertex 3, graph is');
+graph.print();

en/codes/javascript/chapter_graph/graph_bfs.js

@@ -0,0 +1,61 @@
+/**
+ * File: graph_bfs.js
+ * Created Time: 2023-02-21
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+const { GraphAdjList } = require('./graph_adjacency_list');
+const { Vertex } = require('../modules/Vertex');
+
+/* Breadth-first traversal */
+// Use adjacency list to represent the graph, in order to obtain all adjacent vertices of a specified vertex
+function graphBFS(graph, startVet) {
+    // Vertex traversal sequence
+    const res = [];
+    // Hash set for recording vertices that have been visited
+    const visited = new Set();
+    visited.add(startVet);
+    // Queue used to implement BFS
+    const que = [startVet];
+    // Starting from vertex vet, loop until all vertices are visited
+    while (que.length) {
+        const vet = que.shift(); // Dequeue the front vertex
+        res.push(vet); // Record visited vertex
+        // Traverse all adjacent vertices of this vertex
+        for (const adjVet of graph.adjList.get(vet) ?? []) {
+            if (visited.has(adjVet)) {
+                continue; // Skip vertices that have been visited
+            }
+            que.push(adjVet); // Only enqueue unvisited vertices
+            visited.add(adjVet); // Mark this vertex as visited
+        }
+    }
+    // Return vertex traversal sequence
+    return res;
+}
+
+/* Driver Code */
+/* Add edge */
+const v = Vertex.valsToVets([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+const edges = [
+    [v[0], v[1]],
+    [v[0], v[3]],
+    [v[1], v[2]],
+    [v[1], v[4]],
+    [v[2], v[5]],
+    [v[3], v[4]],
+    [v[3], v[6]],
+    [v[4], v[5]],
+    [v[4], v[7]],
+    [v[5], v[8]],
+    [v[6], v[7]],
+    [v[7], v[8]],
+];
+const graph = new GraphAdjList(edges);
+console.log('\nAfter initialization, graph is');
+graph.print();
+
+/* Breadth-first traversal */
+const res = graphBFS(graph, v[0]);
+console.log('\nBreadth-first traversal (BFS) vertex sequence is');
+console.log(Vertex.vetsToVals(res));

en/codes/javascript/chapter_graph/graph_dfs.js

@@ -0,0 +1,54 @@
+/**
+ * File: graph_dfs.js
+ * Created Time: 2023-02-21
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+const { Vertex } = require('../modules/Vertex');
+const { GraphAdjList } = require('./graph_adjacency_list');
+
+/* Depth-first traversal */
+// Use adjacency list to represent the graph, in order to obtain all adjacent vertices of a specified vertex
+function dfs(graph, visited, res, vet) {
+    res.push(vet); // Record visited vertex
+    visited.add(vet); // Mark this vertex as visited
+    // Traverse all adjacent vertices of this vertex
+    for (const adjVet of graph.adjList.get(vet)) {
+        if (visited.has(adjVet)) {
+            continue; // Skip vertices that have been visited
+        }
+        // Recursively visit adjacent vertices
+        dfs(graph, visited, res, adjVet);
+    }
+}
+
+/* Depth-first traversal */
+// Use adjacency list to represent the graph, in order to obtain all adjacent vertices of a specified vertex
+function graphDFS(graph, startVet) {
+    // Vertex traversal sequence
+    const res = [];
+    // Hash set for recording vertices that have been visited
+    const visited = new Set();
+    dfs(graph, visited, res, startVet);
+    return res;
+}
+
+/* Driver Code */
+/* Add edge */
+const v = Vertex.valsToVets([0, 1, 2, 3, 4, 5, 6]);
+const edges = [
+    [v[0], v[1]],
+    [v[0], v[3]],
+    [v[1], v[2]],
+    [v[2], v[5]],
+    [v[4], v[5]],
+    [v[5], v[6]],
+];
+const graph = new GraphAdjList(edges);
+console.log('\nAfter initialization, graph is');
+graph.print();
+
+/* Depth-first traversal */
+const res = graphDFS(graph, v[0]);
+console.log('\nDepth-first traversal (DFS) vertex sequence is');
+console.log(Vertex.vetsToVals(res));

en/codes/javascript/chapter_greedy/coin_change_greedy.js

@@ -0,0 +1,48 @@
+/**
+ * File: coin_change_greedy.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Coin change: Greedy algorithm */
+function coinChangeGreedy(coins, amt) {
+    // Assume coins array is sorted
+    let i = coins.length - 1;
+    let count = 0;
+    // Loop to make greedy choices until no remaining amount
+    while (amt > 0) {
+        // Find the coin that is less than and closest to the remaining amount
+        while (i > 0 && coins[i] > amt) {
+            i--;
+        }
+        // Choose coins[i]
+        amt -= coins[i];
+        count++;
+    }
+    // If no feasible solution is found, return -1
+    return amt === 0 ? count : -1;
+}
+
+/* Driver Code */
+// Greedy algorithm: Can guarantee finding the global optimal solution
+let coins = [1, 5, 10, 20, 50, 100];
+let amt = 186;
+let res = coinChangeGreedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`Minimum coins needed to make ${amt} is ${res}`);
+
+// Greedy algorithm: Cannot guarantee finding the global optimal solution
+coins = [1, 20, 50];
+amt = 60;
+res = coinChangeGreedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`Minimum coins needed to make ${amt} is ${res}`);
+console.log('Actually the minimum number needed is 3, i.e., 20 + 20 + 20');
+
+// Greedy algorithm: Cannot guarantee finding the global optimal solution
+coins = [1, 49, 50];
+amt = 98;
+res = coinChangeGreedy(coins, amt);
+console.log(`\ncoins = ${coins}, amt = ${amt}`);
+console.log(`Minimum coins needed to make ${amt} is ${res}`);
+console.log('Actually the minimum number needed is 2, i.e., 49 + 49');

en/codes/javascript/chapter_greedy/fractional_knapsack.js

@@ -0,0 +1,46 @@
+/**
+ * File: fractional_knapsack.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Item */
+class Item {
+    constructor(w, v) {
+        this.w = w; // Item weight
+        this.v = v; // Item value
+    }
+}
+
+/* Fractional knapsack: Greedy algorithm */
+function fractionalKnapsack(wgt, val, cap) {
+    // Create item list with two attributes: weight, value
+    const items = wgt.map((w, i) => new Item(w, val[i]));
+    // Sort by unit value item.v / item.w from high to low
+    items.sort((a, b) => b.v / b.w - a.v / a.w);
+    // Loop for greedy selection
+    let res = 0;
+    for (const item of items) {
+        if (item.w <= cap) {
+            // If remaining capacity is sufficient, put the entire current item into the knapsack
+            res += item.v;
+            cap -= item.w;
+        } else {
+            // If remaining capacity is insufficient, put part of the current item into the knapsack
+            res += (item.v / item.w) * cap;
+            // No remaining capacity, so break out of the loop
+            break;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const wgt = [10, 20, 30, 40, 50];
+const val = [50, 120, 150, 210, 240];
+const cap = 50;
+const n = wgt.length;
+
+// Greedy algorithm
+const res = fractionalKnapsack(wgt, val, cap);
+console.log(`Maximum item value not exceeding knapsack capacity is ${res}`);

en/codes/javascript/chapter_greedy/max_capacity.js

@@ -0,0 +1,34 @@
+/**
+ * File: max_capacity.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Max capacity: Greedy algorithm */
+function maxCapacity(ht) {
+    // Initialize i, j to be at both ends of the array
+    let i = 0,
+        j = ht.length - 1;
+    // Initial max capacity is 0
+    let res = 0;
+    // Loop for greedy selection until the two boards meet
+    while (i < j) {
+        // Update max capacity
+        const cap = Math.min(ht[i], ht[j]) * (j - i);
+        res = Math.max(res, cap);
+        // Move the shorter board inward
+        if (ht[i] < ht[j]) {
+            i += 1;
+        } else {
+            j -= 1;
+        }
+    }
+    return res;
+}
+
+/* Driver Code */
+const ht = [3, 8, 5, 2, 7, 7, 3, 4];
+
+// Greedy algorithm
+const res = maxCapacity(ht);
+console.log(`Maximum capacity is ${res}`);

en/codes/javascript/chapter_greedy/max_product_cutting.js

@@ -0,0 +1,33 @@
+/**
+ * File: max_product_cutting.js
+ * Created Time: 2023-09-02
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Max product cutting: Greedy algorithm */
+function maxProductCutting(n) {
+    // When n <= 3, must cut out a 1
+    if (n <= 3) {
+        return 1 * (n - 1);
+    }
+    // Greedily cut out 3, a is the number of 3s, b is the remainder
+    let a = Math.floor(n / 3);
+    let b = n % 3;
+    if (b === 1) {
+        // When the remainder is 1, convert a pair of 1 * 3 to 2 * 2
+        return Math.pow(3, a - 1) * 2 * 2;
+    }
+    if (b === 2) {
+        // When the remainder is 2, do nothing
+        return Math.pow(3, a) * 2;
+    }
+    // When the remainder is 0, do nothing
+    return Math.pow(3, a);
+}
+
+/* Driver Code */
+let n = 58;
+
+// Greedy algorithm
+let res = maxProductCutting(n);
+console.log(`Maximum cutting product is ${res}`);

en/codes/javascript/chapter_hashing/array_hash_map.js

@@ -0,0 +1,128 @@
+/**
+ * File: array_hash_map.js
+ * Created Time: 2022-12-26
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Key-value pair Number -> String */
+class Pair {
+    constructor(key, val) {
+        this.key = key;
+        this.val = val;
+    }
+}
+
+/* Hash table based on array implementation */
+class ArrayHashMap {
+    #buckets;
+    constructor() {
+        // Initialize array with 100 buckets
+        this.#buckets = new Array(100).fill(null);
+    }
+
+    /* Hash function */
+    #hashFunc(key) {
+        return key % 100;
+    }
+
+    /* Query operation */
+    get(key) {
+        let index = this.#hashFunc(key);
+        let pair = this.#buckets[index];
+        if (pair === null) return null;
+        return pair.val;
+    }
+
+    /* Add operation */
+    set(key, val) {
+        let index = this.#hashFunc(key);
+        this.#buckets[index] = new Pair(key, val);
+    }
+
+    /* Remove operation */
+    delete(key) {
+        let index = this.#hashFunc(key);
+        // Set to null to represent deletion
+        this.#buckets[index] = null;
+    }
+
+    /* Get all key-value pairs */
+    entries() {
+        let arr = [];
+        for (let i = 0; i < this.#buckets.length; i++) {
+            if (this.#buckets[i]) {
+                arr.push(this.#buckets[i]);
+            }
+        }
+        return arr;
+    }
+
+    /* Get all keys */
+    keys() {
+        let arr = [];
+        for (let i = 0; i < this.#buckets.length; i++) {
+            if (this.#buckets[i]) {
+                arr.push(this.#buckets[i].key);
+            }
+        }
+        return arr;
+    }
+
+    /* Get all values */
+    values() {
+        let arr = [];
+        for (let i = 0; i < this.#buckets.length; i++) {
+            if (this.#buckets[i]) {
+                arr.push(this.#buckets[i].val);
+            }
+        }
+        return arr;
+    }
+
+    /* Print hash table */
+    print() {
+        let pairSet = this.entries();
+        for (const pair of pairSet) {
+            console.info(`${pair.key} -> ${pair.val}`);
+        }
+    }
+}
+
+/* Driver Code */
+/* Initialize hash table */
+const map = new ArrayHashMap();
+/* Add operation */
+// Add key-value pair (key, value) to the hash table
+map.set(12836, 'Xiao Ha');
+map.set(15937, 'Xiao Luo');
+map.set(16750, 'Xiao Suan');
+map.set(13276, 'Xiao Fa');
+map.set(10583, 'Xiao Ya');
+console.info('\nAfter adding is complete, hash table is\nKey -> Value');
+map.print();
+
+/* Query operation */
+// Input key into hash table to get value
+let name = map.get(15937);
+console.info('\nInput student ID 15937, query name ' + name);
+
+/* Remove operation */
+// Remove key-value pair (key, value) from hash table
+map.delete(10583);
+console.info('\nAfter removing 10583, hash table is\nKey -> Value');
+map.print();
+
+/* Traverse hash table */
+console.info('\nTraverse key-value pairs Key->Value');
+for (const pair of map.entries()) {
+    if (!pair) continue;
+    console.info(pair.key + ' -> ' + pair.val);
+}
+console.info('\nTraverse keys only Key');
+for (const key of map.keys()) {
+    console.info(key);
+}
+console.info('\nTraverse values only Value');
+for (const val of map.values()) {
+    console.info(val);
+}

en/codes/javascript/chapter_hashing/hash_map.js

@@ -0,0 +1,44 @@
+/**
+ * File: hash_map.js
+ * Created Time: 2022-12-26
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Driver Code */
+/* Initialize hash table */
+const map = new Map();
+
+/* Add operation */
+// Add key-value pair (key, value) to the hash table
+map.set(12836, 'Xiao Ha');
+map.set(15937, 'Xiao Luo');
+map.set(16750, 'Xiao Suan');
+map.set(13276, 'Xiao Fa');
+map.set(10583, 'Xiao Ya');
+console.info('\nAfter adding is complete, hash table is\nKey -> Value');
+console.info(map);
+
+/* Query operation */
+// Input key into hash table to get value
+let name = map.get(15937);
+console.info('\nInput student ID 15937, query name ' + name);
+
+/* Remove operation */
+// Remove key-value pair (key, value) from hash table
+map.delete(10583);
+console.info('\nAfter removing 10583, hash table is\nKey -> Value');
+console.info(map);
+
+/* Traverse hash table */
+console.info('\nTraverse key-value pairs Key->Value');
+for (const [k, v] of map.entries()) {
+    console.info(k + ' -> ' + v);
+}
+console.info('\nTraverse keys only Key');
+for (const k of map.keys()) {
+    console.info(k);
+}
+console.info('\nTraverse values only Value');
+for (const v of map.values()) {
+    console.info(v);
+}

en/codes/javascript/chapter_hashing/hash_map_chaining.js

@@ -0,0 +1,142 @@
+/**
+ * File: hash_map_chaining.js
+ * Created Time: 2023-08-06
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Key-value pair Number -> String */
+class Pair {
+    constructor(key, val) {
+        this.key = key;
+        this.val = val;
+    }
+}
+
+/* Hash table with separate chaining */
+class HashMapChaining {
+    #size; // Number of key-value pairs
+    #capacity; // Hash table capacity
+    #loadThres; // Load factor threshold for triggering expansion
+    #extendRatio; // Expansion multiplier
+    #buckets; // Bucket array
+
+    /* Constructor */
+    constructor() {
+        this.#size = 0;
+        this.#capacity = 4;
+        this.#loadThres = 2.0 / 3.0;
+        this.#extendRatio = 2;
+        this.#buckets = new Array(this.#capacity).fill(null).map((x) => []);
+    }
+
+    /* Hash function */
+    #hashFunc(key) {
+        return key % this.#capacity;
+    }
+
+    /* Load factor */
+    #loadFactor() {
+        return this.#size / this.#capacity;
+    }
+
+    /* Query operation */
+    get(key) {
+        const index = this.#hashFunc(key);
+        const bucket = this.#buckets[index];
+        // Traverse bucket, if key is found, return corresponding val
+        for (const pair of bucket) {
+            if (pair.key === key) {
+                return pair.val;
+            }
+        }
+        // If key is not found, return null
+        return null;
+    }
+
+    /* Add operation */
+    put(key, val) {
+        // When load factor exceeds threshold, perform expansion
+        if (this.#loadFactor() > this.#loadThres) {
+            this.#extend();
+        }
+        const index = this.#hashFunc(key);
+        const bucket = this.#buckets[index];
+        // Traverse bucket, if specified key is encountered, update corresponding val and return
+        for (const pair of bucket) {
+            if (pair.key === key) {
+                pair.val = val;
+                return;
+            }
+        }
+        // If key does not exist, append key-value pair to the end
+        const pair = new Pair(key, val);
+        bucket.push(pair);
+        this.#size++;
+    }
+
+    /* Remove operation */
+    remove(key) {
+        const index = this.#hashFunc(key);
+        let bucket = this.#buckets[index];
+        // Traverse bucket and remove key-value pair from it
+        for (let i = 0; i < bucket.length; i++) {
+            if (bucket[i].key === key) {
+                bucket.splice(i, 1);
+                this.#size--;
+                break;
+            }
+        }
+    }
+
+    /* Expand hash table */
+    #extend() {
+        // Temporarily store the original hash table
+        const bucketsTmp = this.#buckets;
+        // Initialize expanded new hash table
+        this.#capacity *= this.#extendRatio;
+        this.#buckets = new Array(this.#capacity).fill(null).map((x) => []);
+        this.#size = 0;
+        // Move key-value pairs from original hash table to new hash table
+        for (const bucket of bucketsTmp) {
+            for (const pair of bucket) {
+                this.put(pair.key, pair.val);
+            }
+        }
+    }
+
+    /* Print hash table */
+    print() {
+        for (const bucket of this.#buckets) {
+            let res = [];
+            for (const pair of bucket) {
+                res.push(pair.key + ' -> ' + pair.val);
+            }
+            console.log(res);
+        }
+    }
+}
+
+/* Driver Code */
+/* Initialize hash table */
+const map = new HashMapChaining();
+
+/* Add operation */
+// Add key-value pair (key, value) to the hash table
+map.put(12836, 'Xiao Ha');
+map.put(15937, 'Xiao Luo');
+map.put(16750, 'Xiao Suan');
+map.put(13276, 'Xiao Fa');
+map.put(10583, 'Xiao Ya');
+console.log('\nAfter adding is complete, hash table is\nKey -> Value');
+map.print();
+
+/* Query operation */
+// Input key into hash table to get value
+const name = map.get(13276);
+console.log('\nInput student ID 13276, query name ' + name);
+
+/* Remove operation */
+// Remove key-value pair (key, value) from hash table
+map.remove(12836);
+console.log('\nAfter removing 12836, hash table is\nKey -> Value');
+map.print();

en/codes/javascript/chapter_hashing/hash_map_open_addressing.js

@@ -0,0 +1,177 @@
+/**
+ * File: hashMapOpenAddressing.js
+ * Created Time: 2023-06-13
+ * Author: yuan0221 (yl1452491917@gmail.com), krahets (krahets@163.com)
+ */
+
+/* Key-value pair Number -> String */
+class Pair {
+    constructor(key, val) {
+        this.key = key;
+        this.val = val;
+    }
+}
+
+/* Hash table with open addressing */
+class HashMapOpenAddressing {
+    #size; // Number of key-value pairs
+    #capacity; // Hash table capacity
+    #loadThres; // Load factor threshold for triggering expansion
+    #extendRatio; // Expansion multiplier
+    #buckets; // Bucket array
+    #TOMBSTONE; // Removal marker
+
+    /* Constructor */
+    constructor() {
+        this.#size = 0; // Number of key-value pairs
+        this.#capacity = 4; // Hash table capacity
+        this.#loadThres = 2.0 / 3.0; // Load factor threshold for triggering expansion
+        this.#extendRatio = 2; // Expansion multiplier
+        this.#buckets = Array(this.#capacity).fill(null); // Bucket array
+        this.#TOMBSTONE = new Pair(-1, '-1'); // Removal marker
+    }
+
+    /* Hash function */
+    #hashFunc(key) {
+        return key % this.#capacity;
+    }
+
+    /* Load factor */
+    #loadFactor() {
+        return this.#size / this.#capacity;
+    }
+
+    /* Search for bucket index corresponding to key */
+    #findBucket(key) {
+        let index = this.#hashFunc(key);
+        let firstTombstone = -1;
+        // Linear probing, break when encountering an empty bucket
+        while (this.#buckets[index] !== null) {
+            // If key is encountered, return the corresponding bucket index
+            if (this.#buckets[index].key === key) {
+                // If a removal marker was encountered before, move the key-value pair to that index
+                if (firstTombstone !== -1) {
+                    this.#buckets[firstTombstone] = this.#buckets[index];
+                    this.#buckets[index] = this.#TOMBSTONE;
+                    return firstTombstone; // Return the moved bucket index
+                }
+                return index; // Return bucket index
+            }
+            // Record the first removal marker encountered
+            if (
+                firstTombstone === -1 &&
+                this.#buckets[index] === this.#TOMBSTONE
+            ) {
+                firstTombstone = index;
+            }
+            // Calculate bucket index, wrap around to the head if past the tail
+            index = (index + 1) % this.#capacity;
+        }
+        // If key does not exist, return the index for insertion
+        return firstTombstone === -1 ? index : firstTombstone;
+    }
+
+    /* Query operation */
+    get(key) {
+        // Search for bucket index corresponding to key
+        const index = this.#findBucket(key);
+        // If key-value pair is found, return corresponding val
+        if (
+            this.#buckets[index] !== null &&
+            this.#buckets[index] !== this.#TOMBSTONE
+        ) {
+            return this.#buckets[index].val;
+        }
+        // If key-value pair does not exist, return null
+        return null;
+    }
+
+    /* Add operation */
+    put(key, val) {
+        // When load factor exceeds threshold, perform expansion
+        if (this.#loadFactor() > this.#loadThres) {
+            this.#extend();
+        }
+        // Search for bucket index corresponding to key
+        const index = this.#findBucket(key);
+        // If key-value pair is found, overwrite val and return
+        if (
+            this.#buckets[index] !== null &&
+            this.#buckets[index] !== this.#TOMBSTONE
+        ) {
+            this.#buckets[index].val = val;
+            return;
+        }
+        // If key-value pair does not exist, add the key-value pair
+        this.#buckets[index] = new Pair(key, val);
+        this.#size++;
+    }
+
+    /* Remove operation */
+    remove(key) {
+        // Search for bucket index corresponding to key
+        const index = this.#findBucket(key);
+        // If key-value pair is found, overwrite it with removal marker
+        if (
+            this.#buckets[index] !== null &&
+            this.#buckets[index] !== this.#TOMBSTONE
+        ) {
+            this.#buckets[index] = this.#TOMBSTONE;
+            this.#size--;
+        }
+    }
+
+    /* Expand hash table */
+    #extend() {
+        // Temporarily store the original hash table
+        const bucketsTmp = this.#buckets;
+        // Initialize expanded new hash table
+        this.#capacity *= this.#extendRatio;
+        this.#buckets = Array(this.#capacity).fill(null);
+        this.#size = 0;
+        // Move key-value pairs from original hash table to new hash table
+        for (const pair of bucketsTmp) {
+            if (pair !== null && pair !== this.#TOMBSTONE) {
+                this.put(pair.key, pair.val);
+            }
+        }
+    }
+
+    /* Print hash table */
+    print() {
+        for (const pair of this.#buckets) {
+            if (pair === null) {
+                console.log('null');
+            } else if (pair === this.#TOMBSTONE) {
+                console.log('TOMBSTONE');
+            } else {
+                console.log(pair.key + ' -> ' + pair.val);
+            }
+        }
+    }
+}
+
+/* Driver Code */
+// Initialize hash table
+const hashmap = new HashMapOpenAddressing();
+
+// Add operation
+// Add key-value pair (key, val) to the hash table
+hashmap.put(12836, 'Xiao Ha');
+hashmap.put(15937, 'Xiao Luo');
+hashmap.put(16750, 'Xiao Suan');
+hashmap.put(13276, 'Xiao Fa');
+hashmap.put(10583, 'Xiao Ya');
+console.log('\nAfter adding is complete, hash table is\nKey -> Value');
+hashmap.print();
+
+// Query operation
+// Input key into hash table to get value val
+const name = hashmap.get(13276);
+console.log('\nInput student ID 13276, query name ' + name);
+
+// Remove operation
+// Remove key-value pair (key, val) from hash table
+hashmap.remove(16750);
+console.log('\nAfter removing 16750, hash table is\nKey -> Value');
+hashmap.print();

en/codes/javascript/chapter_hashing/simple_hash.js

@@ -0,0 +1,60 @@
+/**
+ * File: simple_hash.js
+ * Created Time: 2023-08-06
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+/* Additive hash */
+function addHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash = (hash + c.charCodeAt(0)) % MODULUS;
+    }
+    return hash;
+}
+
+/* Multiplicative hash */
+function mulHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash = (31 * hash + c.charCodeAt(0)) % MODULUS;
+    }
+    return hash;
+}
+
+/* XOR hash */
+function xorHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash ^= c.charCodeAt(0);
+    }
+    return hash % MODULUS;
+}
+
+/* Rotational hash */
+function rotHash(key) {
+    let hash = 0;
+    const MODULUS = 1000000007;
+    for (const c of key) {
+        hash = ((hash << 4) ^ (hash >> 28) ^ c.charCodeAt(0)) % MODULUS;
+    }
+    return hash;
+}
+
+/* Driver Code */
+const key = 'Hello Algo';
+
+let hash = addHash(key);
+console.log('Additive hash value is ' + hash);
+
+hash = mulHash(key);
+console.log('Multiplicative hash value is ' + hash);
+
+hash = xorHash(key);
+console.log('XOR hash value is ' + hash);
+
+hash = rotHash(key);
+console.log('Rotational hash value is ' + hash);

en/codes/javascript/chapter_heap/my_heap.js

@@ -0,0 +1,158 @@
+/**
+ * File: my_heap.js
+ * Created Time: 2023-02-06
+ * Author: what-is-me (whatisme@outlook.jp)
+ */
+
+const { printHeap } = require('../modules/PrintUtil');
+
+/* Max heap class */
+class MaxHeap {
+    #maxHeap;
+
+    /* Constructor, build empty heap or build heap from input list */
+    constructor(nums) {
+        // Add list elements to heap as is
+        this.#maxHeap = nums === undefined ? [] : [...nums];
+        // Heapify all nodes except leaf nodes
+        for (let i = this.#parent(this.size() - 1); i >= 0; i--) {
+            this.#siftDown(i);
+        }
+    }
+
+    /* Get index of left child node */
+    #left(i) {
+        return 2 * i + 1;
+    }
+
+    /* Get index of right child node */
+    #right(i) {
+        return 2 * i + 2;
+    }
+
+    /* Get index of parent node */
+    #parent(i) {
+        return Math.floor((i - 1) / 2); // Floor division
+    }
+
+    /* Swap elements */
+    #swap(i, j) {
+        const tmp = this.#maxHeap[i];
+        this.#maxHeap[i] = this.#maxHeap[j];
+        this.#maxHeap[j] = tmp;
+    }
+
+    /* Get heap size */
+    size() {
+        return this.#maxHeap.length;
+    }
+
+    /* Check if heap is empty */
+    isEmpty() {
+        return this.size() === 0;
+    }
+
+    /* Access top element */
+    peek() {
+        return this.#maxHeap[0];
+    }
+
+    /* Element enters heap */
+    push(val) {
+        // Add node
+        this.#maxHeap.push(val);
+        // Heapify from bottom to top
+        this.#siftUp(this.size() - 1);
+    }
+
+    /* Starting from node i, heapify from bottom to top */
+    #siftUp(i) {
+        while (true) {
+            // Get parent node of node i
+            const p = this.#parent(i);
+            // When "crossing root node" or "node needs no repair", end heapify
+            if (p < 0 || this.#maxHeap[i] <= this.#maxHeap[p]) break;
+            // Swap two nodes
+            this.#swap(i, p);
+            // Loop upward heapify
+            i = p;
+        }
+    }
+
+    /* Element exits heap */
+    pop() {
+        // Handle empty case
+        if (this.isEmpty()) throw new Error('Heap is empty');
+        // Delete node
+        this.#swap(0, this.size() - 1);
+        // Remove node
+        const val = this.#maxHeap.pop();
+        // Return top element
+        this.#siftDown(0);
+        // Return heap top element
+        return val;
+    }
+
+    /* Starting from node i, heapify from top to bottom */
+    #siftDown(i) {
+        while (true) {
+            // If node i is largest or indices l, r are out of bounds, no need to continue heapify, break
+            const l = this.#left(i),
+                r = this.#right(i);
+            let ma = i;
+            if (l < this.size() && this.#maxHeap[l] > this.#maxHeap[ma]) ma = l;
+            if (r < this.size() && this.#maxHeap[r] > this.#maxHeap[ma]) ma = r;
+            // Swap two nodes
+            if (ma === i) break;
+            // Swap two nodes
+            this.#swap(i, ma);
+            // Loop downwards heapification
+            i = ma;
+        }
+    }
+
+    /* Driver Code */
+    print() {
+        printHeap(this.#maxHeap);
+    }
+
+    /* Extract elements from heap */
+    getMaxHeap() {
+        return this.#maxHeap;
+    }
+}
+
+/* Driver Code */
+if (require.main === module) {
+    /* Consider negating the elements before entering the heap, which can reverse the size relationship, thus implementing max heap */
+    const maxHeap = new MaxHeap([9, 8, 6, 6, 7, 5, 2, 1, 4, 3, 6, 2]);
+    console.log('\nAfter inputting list and building heap');
+    maxHeap.print();
+
+    /* Check if heap is empty */
+    let peek = maxHeap.peek();
+    console.log(`\nHeap top element is ${peek}`);
+
+    /* Element enters heap */
+    let val = 7;
+    maxHeap.push(val);
+    console.log(`\nAfter element ${val} pushes to heap`);
+    maxHeap.print();
+
+    /* Time complexity is O(n), not O(nlogn) */
+    peek = maxHeap.pop();
+    console.log(`\nAfter heap top element ${peek} pops from heap`);
+    maxHeap.print();
+
+    /* Get heap size */
+    let size = maxHeap.size();
+    console.log(`\nHeap size is ${size}`);
+
+    /* Check if heap is empty */
+    let isEmpty = maxHeap.isEmpty();
+    console.log(`\nIs heap empty ${isEmpty}`);
+}
+
+module.exports = {
+    MaxHeap,
+};

en/codes/javascript/chapter_heap/top_k.js

@@ -0,0 +1,58 @@
+/**
+ * File: top_k.js
+ * Created Time: 2023-08-13
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+const { MaxHeap } = require('./my_heap');
+
+/* Element enters heap */
+function pushMinHeap(maxHeap, val) {
+    // Negate element
+    maxHeap.push(-val);
+}
+
+/* Element exits heap */
+function popMinHeap(maxHeap) {
+    // Negate element
+    return -maxHeap.pop();
+}
+
+/* Access top element */
+function peekMinHeap(maxHeap) {
+    // Negate element
+    return -maxHeap.peek();
+}
+
+/* Extract elements from heap */
+function getMinHeap(maxHeap) {
+    // Negate element
+    return maxHeap.getMaxHeap().map((num) => -num);
+}
+
+/* Find the largest k elements in array based on heap */
+function topKHeap(nums, k) {
+    // Python's heapq module implements min heap by default
+    // Note: We negate all heap elements to simulate min heap using max heap
+    const maxHeap = new MaxHeap([]);
+    // Enter the first k elements of array into heap
+    for (let i = 0; i < k; i++) {
+        pushMinHeap(maxHeap, nums[i]);
+    }
+    // Starting from the (k+1)th element, maintain heap length as k
+    for (let i = k; i < nums.length; i++) {
+        // If current element is greater than top element, top element exits heap, current element enters heap
+        if (nums[i] > peekMinHeap(maxHeap)) {
+            popMinHeap(maxHeap);
+            pushMinHeap(maxHeap, nums[i]);
+        }
+    }
+    // Return elements in heap
+    return getMinHeap(maxHeap);
+}
+
+/* Driver Code */
+const nums = [1, 7, 6, 3, 2];
+const k = 3;
+const res = topKHeap(nums, k);
+console.log(`The largest ${k} elements are`, res);

en/codes/javascript/chapter_searching/binary_search.js

@@ -0,0 +1,60 @@
+/**
+ * File: binary_search.js
+ * Created Time: 2022-12-22
+ * Author: JoseHung (szhong@link.cuhk.edu.hk)
+ */
+
+/* Binary search (closed interval on both sides) */
+function binarySearch(nums, target) {
+    // Initialize closed interval [0, n-1], i.e., i, j point to the first and last elements of the array
+    let i = 0,
+        j = nums.length - 1;
+    // Loop, exit when the search interval is empty (empty when i > j)
+    while (i <= j) {
+        // Calculate midpoint index m, use parseInt() to round down
+        const m = parseInt(i + (j - i) / 2);
+        if (nums[m] < target)
+            // This means target is in the interval [m+1, j]
+            i = m + 1;
+        else if (nums[m] > target)
+            // This means target is in the interval [i, m-1]
+            j = m - 1;
+        else return m; // Found the target element, return its index
+    }
+    // Target element not found, return -1
+    return -1;
+}
+
+/* Binary search (left-closed right-open interval) */
+function binarySearchLCRO(nums, target) {
+    // Initialize left-closed right-open interval [0, n), i.e., i, j point to the first element and last element+1
+    let i = 0,
+        j = nums.length;
+    // Loop, exit when the search interval is empty (empty when i = j)
+    while (i < j) {
+        // Calculate midpoint index m, use parseInt() to round down
+        const m = parseInt(i + (j - i) / 2);
+        if (nums[m] < target)
+            // This means target is in the interval [m+1, j)
+            i = m + 1;
+        else if (nums[m] > target)
+            // This means target is in the interval [i, m)
+            j = m;
+        // Found the target element, return its index
+        else return m;
+    }
+    // Target element not found, return -1
+    return -1;
+}
+
+/* Driver Code */
+const target = 6;
+const nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];
+
+/* Binary search (closed interval on both sides) */
+let index = binarySearch(nums, target);
+console.log('Index of target element 6 = ' + index);
+
+/* Binary search (left-closed right-open interval) */
+index = binarySearchLCRO(nums, target);
+console.log('Index of target element 6 = ' + index);

en/codes/javascript/chapter_searching/binary_search_edge.js

@@ -0,0 +1,45 @@
+/**
+ * File: binary_search_edge.js
+ * Created Time: 2023-08-22
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+const { binarySearchInsertion } = require('./binary_search_insertion.js');
+
+/* Binary search for the leftmost target */
+function binarySearchLeftEdge(nums, target) {
+    // Equivalent to finding the insertion point of target
+    const i = binarySearchInsertion(nums, target);
+    // Target not found, return -1
+    if (i === nums.length || nums[i] !== target) {
+        return -1;
+    }
+    // Found target, return index i
+    return i;
+}
+
+/* Binary search for the rightmost target */
+function binarySearchRightEdge(nums, target) {
+    // Convert to finding the leftmost target + 1
+    const i = binarySearchInsertion(nums, target + 1);
+    // j points to the rightmost target, i points to the first element greater than target
+    const j = i - 1;
+    // Target not found, return -1
+    if (j === -1 || nums[j] !== target) {
+        return -1;
+    }
+    // Found target, return index j
+    return j;
+}
+
+/* Driver Code */
+// Array with duplicate elements
+const nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15];
+console.log('\nArray nums = ' + nums);
+// Binary search left and right boundaries
+for (const target of [6, 7]) {
+    let index = binarySearchLeftEdge(nums, target);
+    console.log('Leftmost element ' + target + ' has index ' + index);
+    index = binarySearchRightEdge(nums, target);
+    console.log('Rightmost element ' + target + ' has index ' + index);
+}

en/codes/javascript/chapter_searching/binary_search_insertion.js

@@ -0,0 +1,64 @@
+/**
+ * File: binary_search_insertion.js
+ * Created Time: 2023-08-22
+ * Author: Gaofer Chou (gaofer-chou@qq.com)
+ */
+
+/* Binary search for insertion point (no duplicate elements) */
+function binarySearchInsertionSimple(nums, target) {
+    let i = 0,
+        j = nums.length - 1; // Initialize closed interval [0, n-1]
+    while (i <= j) {
+        const m = Math.floor(i + (j - i) / 2); // Calculate midpoint index m, use Math.floor() to round down
+        if (nums[m] < target) {
+            i = m + 1; // target is in the interval [m+1, j]
+        } else if (nums[m] > target) {
+            j = m - 1; // target is in the interval [i, m-1]
+        } else {
+            return m; // Found target, return insertion point m
+        }
+    }
+    // Target not found, return insertion point i
+    return i;
+}
+
+/* Binary search for insertion point (with duplicate elements) */
+function binarySearchInsertion(nums, target) {
+    let i = 0,
+        j = nums.length - 1; // Initialize closed interval [0, n-1]
+    while (i <= j) {
+        const m = Math.floor(i + (j - i) / 2); // Calculate midpoint index m, use Math.floor() to round down
+        if (nums[m] < target) {
+            i = m + 1; // target is in the interval [m+1, j]
+        } else if (nums[m] > target) {
+            j = m - 1; // target is in the interval [i, m-1]
+        } else {
+            j = m - 1; // The first element less than target is in the interval [i, m-1]
+        }
+    }
+    // Return insertion point i
+    return i;
+}
+
+/* Driver Code */
+// Array without duplicate elements
+let nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35];
+console.log('\nArray nums = ' + nums);
+// Binary search for insertion point
+for (const target of [6, 9]) {
+    const index = binarySearchInsertionSimple(nums, target);
+    console.log('Element ' + target + ''s insertion point index is ' + index);
+}
+
+// Array with duplicate elements
+nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15];
+console.log('\nArray nums = ' + nums);
+// Binary search for insertion point
+for (const target of [2, 6, 20]) {
+    const index = binarySearchInsertion(nums, target);
+    console.log('Element ' + target + ''s insertion point index is ' + index);
+}
+
+module.exports = {
+    binarySearchInsertion,
+};

en/codes/javascript/chapter_searching/hashing_search.js

@@ -0,0 +1,45 @@
+/**
+ * File: hashing_search.js
+ * Created Time: 2022-12-29
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+const { arrToLinkedList } = require('../modules/ListNode');
+
+/* Hash search (array) */
+function hashingSearchArray(map, target) {
+    // Hash table's key: target element, value: index
+    // If this key does not exist in the hash table, return -1
+    return map.has(target) ? map.get(target) : -1;
+}
+
+/* Hash search (linked list) */
+function hashingSearchLinkedList(map, target) {
+    // Hash table key: target node value, value: node object
+    // If key is not in hash table, return null
+    return map.has(target) ? map.get(target) : null;
+}
+
+/* Driver Code */
+const target = 3;
+
+/* Hash search (array) */
+const nums = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8];
+// Initialize hash table
+const map = new Map();
+for (let i = 0; i < nums.length; i++) {
+    map.set(nums[i], i); // key: element, value: index
+}
+const index = hashingSearchArray(map, target);
+console.log('Index of target element 3 = ' + index);
+
+/* Hash search (linked list) */
+let head = arrToLinkedList(nums);
+// Initialize hash table
+const map1 = new Map();
+while (head != null) {
+    map1.set(head.val, head); // key: node value, value: node
+    head = head.next;
+}
+const node = hashingSearchLinkedList(map1, target);
+console.log('Node object with target value 3 is', node);

en/codes/javascript/chapter_searching/linear_search.js

@@ -0,0 +1,47 @@
+/**
+ * File: linear_search.js
+ * Created Time: 2022-12-22
+ * Author: JoseHung (szhong@link.cuhk.edu.hk)
+ */
+
+const { ListNode, arrToLinkedList } = require('../modules/ListNode');
+
+/* Linear search (array) */
+function linearSearchArray(nums, target) {
+    // Traverse array
+    for (let i = 0; i < nums.length; i++) {
+        // Found the target element, return its index
+        if (nums[i] === target) {
+            return i;
+        }
+    }
+    // Target element not found, return -1
+    return -1;
+}
+
+/* Linear search (linked list) */
+function linearSearchLinkedList(head, target) {
+    // Traverse the linked list
+    while (head) {
+        // Found the target node, return it
+        if (head.val === target) {
+            return head;
+        }
+        head = head.next;
+    }
+    // Target node not found, return null
+    return null;
+}
+
+/* Driver Code */
+const target = 3;
+
+/* Perform linear search in array */
+const nums = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8];
+const index = linearSearchArray(nums, target);
+console.log('Index of target element 3 = ' + index);
+
+/* Perform linear search in linked list */
+const head = arrToLinkedList(nums);
+const node = linearSearchLinkedList(head, target);
+console.log('Node object corresponding to target node value 3 is ', node);

en/codes/javascript/chapter_searching/two_sum.js

@@ -0,0 +1,46 @@
+/**
+ * File: two_sum.js
+ * Created Time: 2022-12-15
+ * Author: gyt95 (gytkwan@gmail.com)
+ */
+
+/* Method 1: Brute force enumeration */
+function twoSumBruteForce(nums, target) {
+    const n = nums.length;
+    // Two nested loops, time complexity is O(n^2)
+    for (let i = 0; i < n; i++) {
+        for (let j = i + 1; j < n; j++) {
+            if (nums[i] + nums[j] === target) {
+                return [i, j];
+            }
+        }
+    }
+    return [];
+}
+
+/* Method 2: Auxiliary hash table */
+function twoSumHashTable(nums, target) {
+    // Auxiliary hash table, space complexity is O(n)
+    let m = {};
+    // Single loop, time complexity is O(n)
+    for (let i = 0; i < nums.length; i++) {
+        if (m[target - nums[i]] !== undefined) {
+            return [m[target - nums[i]], i];
+        } else {
+            m[nums[i]] = i;
+        }
+    }
+    return [];
+}
+
+/* Driver Code */
+// Method 1
+const nums = [2, 7, 11, 15],
+    target = 13;
+
+let res = twoSumBruteForce(nums, target);
+console.log('Method 1 res = ', res);
+
+// Method 2
+res = twoSumHashTable(nums, target);
+console.log('Method 2 res = ', res);

en/codes/javascript/chapter_sorting/bubble_sort.js

@@ -0,0 +1,49 @@
+/**
+ * File: bubble_sort.js
+ * Created Time: 2022-12-01
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Bubble sort */
+function bubbleSort(nums) {
+    // Outer loop: unsorted range is [0, i]
+    for (let i = nums.length - 1; i > 0; i--) {
+        // Inner loop: swap the largest element in the unsorted range [0, i] to the rightmost end of that range
+        for (let j = 0; j < i; j++) {
+            if (nums[j] > nums[j + 1]) {
+                // Swap nums[j] and nums[j + 1]
+                let tmp = nums[j];
+                nums[j] = nums[j + 1];
+                nums[j + 1] = tmp;
+            }
+        }
+    }
+}
+
+/* Bubble sort (flag optimization) */
+function bubbleSortWithFlag(nums) {
+    // Outer loop: unsorted range is [0, i]
+    for (let i = nums.length - 1; i > 0; i--) {
+        let flag = false; // Initialize flag
+        // Inner loop: swap the largest element in the unsorted range [0, i] to the rightmost end of that range
+        for (let j = 0; j < i; j++) {
+            if (nums[j] > nums[j + 1]) {
+                // Swap nums[j] and nums[j + 1]
+                let tmp = nums[j];
+                nums[j] = nums[j + 1];
+                nums[j + 1] = tmp;
+                flag = true; // Record element swap
+            }
+        }
+        if (!flag) break; // No elements were swapped in this round of "bubbling", exit directly
+    }
+}
+
+/* Driver Code */
+const nums = [4, 1, 3, 1, 5, 2];
+bubbleSort(nums);
+console.log('After bubble sort, nums =', nums);
+
+const nums1 = [4, 1, 3, 1, 5, 2];
+bubbleSortWithFlag(nums1);
+console.log('After bubble sort, nums =', nums1);

en/codes/javascript/chapter_sorting/bucket_sort.js

@@ -0,0 +1,39 @@
+/**
+ * File: bucket_sort.js
+ * Created Time: 2023-04-08
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Bucket sort */
+function bucketSort(nums) {
+    // Initialize k = n/2 buckets, expected to allocate 2 elements per bucket
+    const k = nums.length / 2;
+    const buckets = [];
+    for (let i = 0; i < k; i++) {
+        buckets.push([]);
+    }
+    // 1. Distribute array elements into various buckets
+    for (const num of nums) {
+        // Input data range is [0, 1), use num * k to map to index range [0, k-1]
+        const i = Math.floor(num * k);
+        // Add num to bucket i
+        buckets[i].push(num);
+    }
+    // 2. Sort each bucket
+    for (const bucket of buckets) {
+        // Use built-in sorting function, can also replace with other sorting algorithms
+        bucket.sort((a, b) => a - b);
+    }
+    // 3. Traverse buckets to merge results
+    let i = 0;
+    for (const bucket of buckets) {
+        for (const num of bucket) {
+            nums[i++] = num;
+        }
+    }
+}
+
+/* Driver Code */
+const nums = [0.49, 0.96, 0.82, 0.09, 0.57, 0.43, 0.91, 0.75, 0.15, 0.37];
+bucketSort(nums);
+console.log('After bucket sort, nums =', nums);

en/codes/javascript/chapter_sorting/counting_sort.js

@@ -0,0 +1,65 @@
+/**
+ * File: counting_sort.js
+ * Created Time: 2023-04-08
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Counting sort */
+// Simple implementation, cannot be used for sorting objects
+function countingSortNaive(nums) {
+    // 1. Count the maximum element m in the array
+    let m = Math.max(...nums);
+    // 2. Count the occurrence of each number
+    // counter[num] represents the occurrence of num
+    const counter = new Array(m + 1).fill(0);
+    for (const num of nums) {
+        counter[num]++;
+    }
+    // 3. Traverse counter, filling each element back into the original array nums
+    let i = 0;
+    for (let num = 0; num < m + 1; num++) {
+        for (let j = 0; j < counter[num]; j++, i++) {
+            nums[i] = num;
+        }
+    }
+}
+
+/* Counting sort */
+// Complete implementation, can sort objects and is a stable sort
+function countingSort(nums) {
+    // 1. Count the maximum element m in the array
+    let m = Math.max(...nums);
+    // 2. Count the occurrence of each number
+    // counter[num] represents the occurrence of num
+    const counter = new Array(m + 1).fill(0);
+    for (const num of nums) {
+        counter[num]++;
+    }
+    // 3. Calculate the prefix sum of counter, converting "occurrence count" to "tail index"
+    // counter[num]-1 is the last index where num appears in res
+    for (let i = 0; i < m; i++) {
+        counter[i + 1] += counter[i];
+    }
+    // 4. Traverse nums in reverse order, placing each element into the result array res
+    // Initialize the array res to record results
+    const n = nums.length;
+    const res = new Array(n);
+    for (let i = n - 1; i >= 0; i--) {
+        const num = nums[i];
+        res[counter[num] - 1] = num; // Place num at the corresponding index
+        counter[num]--; // Decrement the prefix sum by 1, getting the next index to place num
+    }
+    // Use result array res to overwrite the original array nums
+    for (let i = 0; i < n; i++) {
+        nums[i] = res[i];
+    }
+}
+
+/* Driver Code */
+const nums = [1, 0, 1, 2, 0, 4, 0, 2, 2, 4];
+countingSortNaive(nums);
+console.log('After counting sort (cannot sort objects), nums =', nums);
+
+const nums1 = [1, 0, 1, 2, 0, 4, 0, 2, 2, 4];
+countingSort(nums1);
+console.log('After counting sort, nums1 =', nums1);

en/codes/javascript/chapter_sorting/heap_sort.js

@@ -0,0 +1,49 @@
+/**
+ * File: heap_sort.js
+ * Created Time: 2023-06-04
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Heap length is n, start heapifying node i, from top to bottom */
+function siftDown(nums, n, i) {
+    while (true) {
+        // If node i is largest or indices l, r are out of bounds, no need to continue heapify, break
+        let l = 2 * i + 1;
+        let r = 2 * i + 2;
+        let ma = i;
+        if (l < n && nums[l] > nums[ma]) {
+            ma = l;
+        }
+        if (r < n && nums[r] > nums[ma]) {
+            ma = r;
+        }
+        // Swap two nodes
+        if (ma === i) {
+            break;
+        }
+        // Swap two nodes
+        [nums[i], nums[ma]] = [nums[ma], nums[i]];
+        // Loop downwards heapification
+        i = ma;
+    }
+}
+
+/* Heap sort */
+function heapSort(nums) {
+    // Build heap operation: heapify all nodes except leaves
+    for (let i = Math.floor(nums.length / 2) - 1; i >= 0; i--) {
+        siftDown(nums, nums.length, i);
+    }
+    // Extract the largest element from the heap and repeat for n-1 rounds
+    for (let i = nums.length - 1; i > 0; i--) {
+        // Delete node
+        [nums[0], nums[i]] = [nums[i], nums[0]];
+        // Start heapifying the root node, from top to bottom
+        siftDown(nums, i, 0);
+    }
+}
+
+/* Driver Code */
+const nums = [4, 1, 3, 1, 5, 2];
+heapSort(nums);
+console.log('After heap sort, nums =', nums);

en/codes/javascript/chapter_sorting/insertion_sort.js

@@ -0,0 +1,25 @@
+/**
+ * File: insertion_sort.js
+ * Created Time: 2022-12-01
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Insertion sort */
+function insertionSort(nums) {
+    // Outer loop: sorted interval is [0, i-1]
+    for (let i = 1; i < nums.length; i++) {
+        let base = nums[i],
+            j = i - 1;
+        // Inner loop: insert base into the correct position within the sorted interval [0, i-1]
+        while (j >= 0 && nums[j] > base) {
+            nums[j + 1] = nums[j]; // Move nums[j] to the right by one position
+            j--;
+        }
+        nums[j + 1] = base; // Assign base to the correct position
+    }
+}
+
+/* Driver Code */
+const nums = [4, 1, 3, 1, 5, 2];
+insertionSort(nums);
+console.log('After insertion sort, nums =', nums);

en/codes/javascript/chapter_sorting/merge_sort.js

@@ -0,0 +1,52 @@
+/**
+ * File: merge_sort.js
+ * Created Time: 2022-12-01
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Merge left subarray and right subarray */
+function merge(nums, left, mid, right) {
+    // Left subarray interval is [left, mid], right subarray interval is [mid+1, right]
+    // Create a temporary array tmp to store the merged results
+    const tmp = new Array(right - left + 1);
+    // Initialize the start indices of the left and right subarrays
+    let i = left,
+        j = mid + 1,
+        k = 0;
+    // While both subarrays still have elements, compare and copy the smaller element into the temporary array
+    while (i <= mid && j <= right) {
+        if (nums[i] <= nums[j]) {
+            tmp[k++] = nums[i++];
+        } else {
+            tmp[k++] = nums[j++];
+        }
+    }
+    // Copy the remaining elements of the left and right subarrays into the temporary array
+    while (i <= mid) {
+        tmp[k++] = nums[i++];
+    }
+    while (j <= right) {
+        tmp[k++] = nums[j++];
+    }
+    // Copy the elements from the temporary array tmp back to the original array nums at the corresponding interval
+    for (k = 0; k < tmp.length; k++) {
+        nums[left + k] = tmp[k];
+    }
+}
+
+/* Merge sort */
+function mergeSort(nums, left, right) {
+    // Termination condition
+    if (left >= right) return; // Terminate recursion when subarray length is 1
+    // Divide and conquer stage
+    let mid = Math.floor(left + (right - left) / 2); // Calculate midpoint
+    mergeSort(nums, left, mid); // Recursively process the left subarray
+    mergeSort(nums, mid + 1, right); // Recursively process the right subarray
+    // Merge stage
+    merge(nums, left, mid, right);
+}
+
+/* Driver Code */
+const nums = [7, 3, 2, 6, 0, 1, 5, 4];
+mergeSort(nums, 0, nums.length - 1);
+console.log('After merge sort, nums =', nums);

en/codes/javascript/chapter_sorting/quick_sort.js

@@ -0,0 +1,161 @@
+/**
+ * File: quick_sort.js
+ * Created Time: 2022-12-01
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Quick sort class */
+class QuickSort {
+    /* Swap elements */
+    swap(nums, i, j) {
+        let tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+    }
+
+    /* Sentinel partition */
+    partition(nums, left, right) {
+        // Use nums[left] as the pivot
+        let i = left,
+            j = right;
+        while (i < j) {
+            while (i < j && nums[j] >= nums[left]) {
+                j -= 1; // Search from right to left for the first element smaller than the pivot
+            }
+            while (i < j && nums[i] <= nums[left]) {
+                i += 1; // Search from left to right for the first element greater than the pivot
+            }
+            // Swap elements
+            this.swap(nums, i, j); // Swap these two elements
+        }
+        this.swap(nums, i, left); // Swap the pivot to the boundary between the two subarrays
+        return i; // Return the index of the pivot
+    }
+
+    /* Quick sort */
+    quickSort(nums, left, right) {
+        // Terminate recursion when subarray length is 1
+        if (left >= right) return;
+        // Sentinel partition
+        const pivot = this.partition(nums, left, right);
+        // Recursively process the left subarray and right subarray
+        this.quickSort(nums, left, pivot - 1);
+        this.quickSort(nums, pivot + 1, right);
+    }
+}
+
+/* Quick sort class (median pivot optimization) */
+class QuickSortMedian {
+    /* Swap elements */
+    swap(nums, i, j) {
+        let tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+    }
+
+    /* Select the median of three candidate elements */
+    medianThree(nums, left, mid, right) {
+        let l = nums[left],
+            m = nums[mid],
+            r = nums[right];
+        // m is between l and r
+        if ((l <= m && m <= r) || (r <= m && m <= l)) return mid;
+        // l is between m and r
+        if ((m <= l && l <= r) || (r <= l && l <= m)) return left;
+        return right;
+    }
+
+    /* Sentinel partition (median of three) */
+    partition(nums, left, right) {
+        // Select the median of three candidate elements
+        let med = this.medianThree(
+            nums,
+            left,
+            Math.floor((left + right) / 2),
+            right
+        );
+        // Swap the median to the array's leftmost position
+        this.swap(nums, left, med);
+        // Use nums[left] as the pivot
+        let i = left,
+            j = right;
+        while (i < j) {
+            while (i < j && nums[j] >= nums[left]) j--; // Search from right to left for the first element smaller than the pivot
+            while (i < j && nums[i] <= nums[left]) i++; // Search from left to right for the first element greater than the pivot
+            this.swap(nums, i, j); // Swap these two elements
+        }
+        this.swap(nums, i, left); // Swap the pivot to the boundary between the two subarrays
+        return i; // Return the index of the pivot
+    }
+
+    /* Quick sort */
+    quickSort(nums, left, right) {
+        // Terminate recursion when subarray length is 1
+        if (left >= right) return;
+        // Sentinel partition
+        const pivot = this.partition(nums, left, right);
+        // Recursively process the left subarray and right subarray
+        this.quickSort(nums, left, pivot - 1);
+        this.quickSort(nums, pivot + 1, right);
+    }
+}
+
+/* Quick sort class (recursion depth optimization) */
+class QuickSortTailCall {
+    /* Swap elements */
+    swap(nums, i, j) {
+        let tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+    }
+
+    /* Sentinel partition */
+    partition(nums, left, right) {
+        // Use nums[left] as the pivot
+        let i = left,
+            j = right;
+        while (i < j) {
+            while (i < j && nums[j] >= nums[left]) j--; // Search from right to left for the first element smaller than the pivot
+            while (i < j && nums[i] <= nums[left]) i++; // Search from left to right for the first element greater than the pivot
+            this.swap(nums, i, j); // Swap these two elements
+        }
+        this.swap(nums, i, left); // Swap the pivot to the boundary between the two subarrays
+        return i; // Return the index of the pivot
+    }
+
+    /* Quick sort (recursion depth optimization) */
+    quickSort(nums, left, right) {
+        // Terminate when subarray length is 1
+        while (left < right) {
+            // Sentinel partition operation
+            let pivot = this.partition(nums, left, right);
+            // Perform quick sort on the shorter of the two subarrays
+            if (pivot - left < right - pivot) {
+                this.quickSort(nums, left, pivot - 1); // Recursively sort the left subarray
+                left = pivot + 1; // Remaining unsorted interval is [pivot + 1, right]
+            } else {
+                this.quickSort(nums, pivot + 1, right); // Recursively sort the right subarray
+                right = pivot - 1; // Remaining unsorted interval is [left, pivot - 1]
+            }
+        }
+    }
+}
+
+/* Driver Code */
+/* Quick sort */
+const nums = [2, 4, 1, 0, 3, 5];
+const quickSort = new QuickSort();
+quickSort.quickSort(nums, 0, nums.length - 1);
+console.log('After quick sort, nums =', nums);
+
+/* Quick sort (recursion depth optimization) */
+const nums1 = [2, 4, 1, 0, 3, 5];
+const quickSortMedian = new QuickSortMedian();
+quickSortMedian.quickSort(nums1, 0, nums1.length - 1);
+console.log('After quick sort (median pivot optimization), nums =', nums1);
+
+/* Quick sort (recursion depth optimization) */
+const nums2 = [2, 4, 1, 0, 3, 5];
+const quickSortTailCall = new QuickSortTailCall();
+quickSortTailCall.quickSort(nums2, 0, nums2.length - 1);
+console.log('After quick sort (recursion depth optimization), nums =', nums2);

en/codes/javascript/chapter_sorting/radix_sort.js

@@ -0,0 +1,61 @@
+/**
+ * File: radix_sort.js
+ * Created Time: 2023-04-08
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Get the k-th digit of element num, where exp = 10^(k-1) */
+function digit(num, exp) {
+    // Passing exp instead of k can avoid repeated expensive exponentiation here
+    return Math.floor(num / exp) % 10;
+}
+
+/* Counting sort (based on nums k-th digit) */
+function countingSortDigit(nums, exp) {
+    // Decimal digit range is 0~9, therefore need a bucket array of length 10
+    const counter = new Array(10).fill(0);
+    const n = nums.length;
+    // Count the occurrence of digits 0~9
+    for (let i = 0; i < n; i++) {
+        const d = digit(nums[i], exp); // Get the k-th digit of nums[i], noted as d
+        counter[d]++; // Count the occurrence of digit d
+    }
+    // Calculate prefix sum, converting "occurrence count" into "array index"
+    for (let i = 1; i < 10; i++) {
+        counter[i] += counter[i - 1];
+    }
+    // Traverse in reverse, based on bucket statistics, place each element into res
+    const res = new Array(n).fill(0);
+    for (let i = n - 1; i >= 0; i--) {
+        const d = digit(nums[i], exp);
+        const j = counter[d] - 1; // Get the index j for d in the array
+        res[j] = nums[i]; // Place the current element at index j
+        counter[d]--; // Decrease the count of d by 1
+    }
+    // Use result to overwrite the original array nums
+    for (let i = 0; i < n; i++) {
+        nums[i] = res[i];
+    }
+}
+
+/* Radix sort */
+function radixSort(nums) {
+    // Get the maximum element of the array, used to determine the maximum number of digits
+    let m = Math.max(... nums);
+    // Traverse from the lowest to the highest digit
+    for (let exp = 1; exp <= m; exp *= 10) {
+        // Perform counting sort on the k-th digit of array elements
+        // k = 1 -> exp = 1
+        // k = 2 -> exp = 10
+        // i.e., exp = 10^(k-1)
+        countingSortDigit(nums, exp);
+    }
+}
+
+/* Driver Code */
+const nums = [
+    10546151, 35663510, 42865989, 34862445, 81883077, 88906420, 72429244,
+    30524779, 82060337, 63832996,
+];
+radixSort(nums);
+console.log('After radix sort, nums =', nums);

en/codes/javascript/chapter_sorting/selection_sort.js

@@ -0,0 +1,27 @@
+/**
+ * File: selection_sort.js
+ * Created Time: 2023-06-04
+ * Author: Justin (xiefahit@gmail.com)
+ */
+
+/* Selection sort */
+function selectionSort(nums) {
+    let n = nums.length;
+    // Outer loop: unsorted interval is [i, n-1]
+    for (let i = 0; i < n - 1; i++) {
+        // Inner loop: find the smallest element within the unsorted interval
+        let k = i;
+        for (let j = i + 1; j < n; j++) {
+            if (nums[j] < nums[k]) {
+                k = j; // Record the index of the smallest element
+            }
+        }
+        // Swap the smallest element with the first element of the unsorted interval
+        [nums[i], nums[k]] = [nums[k], nums[i]];
+    }
+}
+
+/* Driver Code */
+const nums = [4, 1, 3, 1, 5, 2];
+selectionSort(nums);
+console.log('After selection sort, nums =', nums);

en/codes/javascript/chapter_stack_and_queue/array_deque.js

@@ -0,0 +1,156 @@
+/**
+ * File: array_deque.js
+ * Created Time: 2023-02-28
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+/* Double-ended queue based on circular array implementation */
+class ArrayDeque {
+    #nums; // Array for storing double-ended queue elements
+    #front; // Front pointer, points to the front of the queue element
+    #queSize; // Double-ended queue length
+
+    /* Constructor */
+    constructor(capacity) {
+        this.#nums = new Array(capacity);
+        this.#front = 0;
+        this.#queSize = 0;
+    }
+
+    /* Get the capacity of the double-ended queue */
+    capacity() {
+        return this.#nums.length;
+    }
+
+    /* Get the length of the double-ended queue */
+    size() {
+        return this.#queSize;
+    }
+
+    /* Check if the double-ended queue is empty */
+    isEmpty() {
+        return this.#queSize === 0;
+    }
+
+    /* Calculate circular array index */
+    index(i) {
+        // Use modulo operation to wrap the array head and tail together
+        // When i passes the tail of the array, return to the head
+        // When i passes the head of the array, return to the tail
+        return (i + this.capacity()) % this.capacity();
+    }
+
+    /* Front of the queue enqueue */
+    pushFirst(num) {
+        if (this.#queSize === this.capacity()) {
+            console.log('Double-ended queue is full');
+            return;
+        }
+        // Use modulo operation to wrap front around to the tail after passing the head of the array
+        // Add num to the front of the queue
+        this.#front = this.index(this.#front - 1);
+        // Add num to front of queue
+        this.#nums[this.#front] = num;
+        this.#queSize++;
+    }
+
+    /* Rear of the queue enqueue */
+    pushLast(num) {
+        if (this.#queSize === this.capacity()) {
+            console.log('Double-ended queue is full');
+            return;
+        }
+        // Use modulo operation to wrap rear around to the head after passing the tail of the array
+        const rear = this.index(this.#front + this.#queSize);
+        // Front pointer moves one position backward
+        this.#nums[rear] = num;
+        this.#queSize++;
+    }
+
+    /* Rear of the queue dequeue */
+    popFirst() {
+        const num = this.peekFirst();
+        // Move front pointer backward by one position
+        this.#front = this.index(this.#front + 1);
+        this.#queSize--;
+        return num;
+    }
+
+    /* Access rear of the queue element */
+    popLast() {
+        const num = this.peekLast();
+        this.#queSize--;
+        return num;
+    }
+
+    /* Return list for printing */
+    peekFirst() {
+        if (this.isEmpty()) throw new Error('The Deque Is Empty.');
+        return this.#nums[this.#front];
+    }
+
+    /* Driver Code */
+    peekLast() {
+        if (this.isEmpty()) throw new Error('The Deque Is Empty.');
+        // Initialize double-ended queue
+        const last = this.index(this.#front + this.#queSize - 1);
+        return this.#nums[last];
+    }
+
+    /* Return array for printing */
+    toArray() {
+        // Elements enqueue
+        const res = [];
+        for (let i = 0, j = this.#front; i < this.#queSize; i++, j++) {
+            res[i] = this.#nums[this.index(j)];
+        }
+        return res;
+    }
+}
+
+/* Driver Code */
+/* Get the length of the double-ended queue */
+const capacity = 5;
+const deque = new ArrayDeque(capacity);
+deque.pushLast(3);
+deque.pushLast(2);
+deque.pushLast(5);
+console.log('Deque deque = [' + deque.toArray() + ']');
+
+/* Update element */
+const peekFirst = deque.peekFirst();
+console.log('Front element peekFirst = ' + peekFirst);
+const peekLast = deque.peekLast();
+console.log('Rear element peekLast = ' + peekLast);
+
+/* Elements enqueue */
+deque.pushLast(4);
+console.log('After element 4 enqueues at rear, deque = [' + deque.toArray() + ']');
+deque.pushFirst(1);
+console.log('After element 1 enqueues at front, deque = [' + deque.toArray() + ']');
+
+/* Element dequeue */
+const popLast = deque.popLast();
+console.log(
+    'Rear dequeue element = ' +
+        popLast +
+        ', after rear dequeue deque = [' +
+        deque.toArray() +
+        ']'
+);
+const popFirst = deque.popFirst();
+console.log(
+    'Front dequeue element = ' +
+        popFirst +
+        ', after front dequeue deque = [' +
+        deque.toArray() +
+        ']'
+);
+
+/* Get the length of the double-ended queue */
+const size = deque.size();
+console.log('Double-ended queue length size = ' + size);
+
+/* Check if the double-ended queue is empty */
+const isEmpty = deque.isEmpty();
+console.log('Double-ended queue is empty = ' + isEmpty);

en/codes/javascript/chapter_stack_and_queue/array_queue.js

@@ -0,0 +1,106 @@
+/**
+ * File: array_queue.js
+ * Created Time: 2022-12-13
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+/* Queue based on circular array implementation */
+class ArrayQueue {
+    #nums; // Array for storing queue elements
+    #front = 0; // Front pointer, points to the front of the queue element
+    #queSize = 0; // Queue length
+
+    constructor(capacity) {
+        this.#nums = new Array(capacity);
+    }
+
+    /* Get the capacity of the queue */
+    get capacity() {
+        return this.#nums.length;
+    }
+
+    /* Get the length of the queue */
+    get size() {
+        return this.#queSize;
+    }
+
+    /* Check if the queue is empty */
+    isEmpty() {
+        return this.#queSize === 0;
+    }
+
+    /* Enqueue */
+    push(num) {
+        if (this.size === this.capacity) {
+            console.log('Queue is full');
+            return;
+        }
+        // Use modulo operation to wrap rear around to the head after passing the tail of the array
+        // Add num to the rear of the queue
+        const rear = (this.#front + this.size) % this.capacity;
+        // Front pointer moves one position backward
+        this.#nums[rear] = num;
+        this.#queSize++;
+    }
+
+    /* Dequeue */
+    pop() {
+        const num = this.peek();
+        // Move front pointer backward by one position, if it passes the tail, return to array head
+        this.#front = (this.#front + 1) % this.capacity;
+        this.#queSize--;
+        return num;
+    }
+
+    /* Return list for printing */
+    peek() {
+        if (this.isEmpty()) throw new Error('Queue is empty');
+        return this.#nums[this.#front];
+    }
+
+    /* Return Array */
+    toArray() {
+        // Elements enqueue
+        const arr = new Array(this.size);
+        for (let i = 0, j = this.#front; i < this.size; i++, j++) {
+            arr[i] = this.#nums[j % this.capacity];
+        }
+        return arr;
+    }
+}
+
+/* Driver Code */
+/* Access front of the queue element */
+const capacity = 10;
+const queue = new ArrayQueue(capacity);
+
+/* Elements enqueue */
+queue.push(1);
+queue.push(3);
+queue.push(2);
+queue.push(5);
+queue.push(4);
+console.log('Queue queue =', queue.toArray());
+
+/* Return list for printing */
+const peek = queue.peek();
+console.log('Front element peek = ' + peek);
+
+/* Element dequeue */
+const pop = queue.pop();
+console.log('Dequeue element pop = ' + pop + ', after dequeue queue =', queue.toArray());
+
+/* Get the length of the queue */
+const size = queue.size;
+console.log('Queue length size = ' + size);
+
+/* Check if the queue is empty */
+const isEmpty = queue.isEmpty();
+console.log('Queue is empty = ' + isEmpty);
+
+/* Test circular array */
+for (let i = 0; i < 10; i++) {
+    queue.push(i);
+    queue.pop();
+    console.log('Round ' + i + ' rounds of enqueue + dequeue, queue =', queue.toArray());
+}

en/codes/javascript/chapter_stack_and_queue/array_stack.js

@@ -0,0 +1,75 @@
+/**
+ * File: array_stack.js
+ * Created Time: 2022-12-09
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+/* Stack based on array implementation */
+class ArrayStack {
+    #stack;
+    constructor() {
+        this.#stack = [];
+    }
+
+    /* Get the length of the stack */
+    get size() {
+        return this.#stack.length;
+    }
+
+    /* Check if the stack is empty */
+    isEmpty() {
+        return this.#stack.length === 0;
+    }
+
+    /* Push */
+    push(num) {
+        this.#stack.push(num);
+    }
+
+    /* Pop */
+    pop() {
+        if (this.isEmpty()) throw new Error('Stack is empty');
+        return this.#stack.pop();
+    }
+
+    /* Return list for printing */
+    top() {
+        if (this.isEmpty()) throw new Error('Stack is empty');
+        return this.#stack[this.#stack.length - 1];
+    }
+
+    /* Return Array */
+    toArray() {
+        return this.#stack;
+    }
+}
+
+/* Driver Code */
+/* Access top of the stack element */
+const stack = new ArrayStack();
+
+/* Elements push onto stack */
+stack.push(1);
+stack.push(3);
+stack.push(2);
+stack.push(5);
+stack.push(4);
+console.log('Stack stack = ');
+console.log(stack.toArray());
+
+/* Return list for printing */
+const top = stack.top();
+console.log('Stack top element top = ' + top);
+
+/* Element pop from stack */
+const pop = stack.pop();
+console.log('Pop element pop = ' + pop + ', after pop, stack = ');
+console.log(stack.toArray());
+
+/* Get the length of the stack */
+const size = stack.size;
+console.log('Stack length size = ' + size);
+
+/* Check if empty */
+const isEmpty = stack.isEmpty();
+console.log('Stack is empty = ' + isEmpty);

en/codes/javascript/chapter_stack_and_queue/deque.js

@@ -0,0 +1,44 @@
+/**
+ * File: deque.js
+ * Created Time: 2023-01-17
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+/* Driver Code */
+/* Get the length of the double-ended queue */
+// JavaScript has no built-in deque, can only use Array as deque
+const deque = [];
+
+/* Elements enqueue */
+deque.push(2);
+deque.push(5);
+deque.push(4);
+// Note: due to array, unshift() method has O(n) time complexity
+deque.unshift(3);
+deque.unshift(1);
+console.log('Double-ended queue deque = ', deque);
+
+/* Update element */
+const peekFirst = deque[0];
+console.log('Front element peekFirst = ' + peekFirst);
+const peekLast = deque[deque.length - 1];
+console.log('Rear element peekLast = ' + peekLast);
+
+/* Element dequeue */
+// Note: due to array, shift() method has O(n) time complexity
+const popFront = deque.shift();
+console.log(
+    'Front dequeue element popFront = ' + popFront + ', after front dequeue, deque = ' + deque
+);
+const popBack = deque.pop();
+console.log(
+    'Dequeue rear element popBack = ' + popBack + ', after rear dequeue, deque = ' + deque
+);
+
+/* Get the length of the double-ended queue */
+const size = deque.length;
+console.log('Double-ended queue length size = ' + size);
+
+/* Check if the double-ended queue is empty */
+const isEmpty = size === 0;
+console.log('Double-ended queue is empty = ' + isEmpty);

en/codes/javascript/chapter_stack_and_queue/linkedlist_deque.js

@@ -0,0 +1,167 @@
+/**
+ * File: linkedlist_deque.js
+ * Created Time: 2023-02-04
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+/* Doubly linked list node */
+class ListNode {
+    prev; // Predecessor node reference (pointer)
+    next; // Successor node reference (pointer)
+    val; // Node value
+
+    constructor(val) {
+        this.val = val;
+        this.next = null;
+        this.prev = null;
+    }
+}
+
+/* Double-ended queue based on doubly linked list implementation */
+class LinkedListDeque {
+    #front; // Head node front
+    #rear; // Tail node rear
+    #queSize; // Length of the double-ended queue
+
+    constructor() {
+        this.#front = null;
+        this.#rear = null;
+        this.#queSize = 0;
+    }
+
+    /* Rear of the queue enqueue operation */
+    pushLast(val) {
+        const node = new ListNode(val);
+        // If the linked list is empty, make both front and rear point to node
+        if (this.#queSize === 0) {
+            this.#front = node;
+            this.#rear = node;
+        } else {
+            // Add node to the tail of the linked list
+            this.#rear.next = node;
+            node.prev = this.#rear;
+            this.#rear = node; // Update tail node
+        }
+        this.#queSize++;
+    }
+
+    /* Front of the queue enqueue operation */
+    pushFirst(val) {
+        const node = new ListNode(val);
+        // If the linked list is empty, make both front and rear point to node
+        if (this.#queSize === 0) {
+            this.#front = node;
+            this.#rear = node;
+        } else {
+            // Add node to the head of the linked list
+            this.#front.prev = node;
+            node.next = this.#front;
+            this.#front = node; // Update head node
+        }
+        this.#queSize++;
+    }
+
+    /* Temporarily store tail node value */
+    popLast() {
+        if (this.#queSize === 0) {
+            return null;
+        }
+        const value = this.#rear.val; // Store tail node value
+        // Update tail node
+        let temp = this.#rear.prev;
+        if (temp !== null) {
+            temp.next = null;
+            this.#rear.prev = null;
+        }
+        this.#rear = temp; // Update tail node
+        this.#queSize--;
+        return value;
+    }
+
+    /* Temporarily store head node value */
+    popFirst() {
+        if (this.#queSize === 0) {
+            return null;
+        }
+        const value = this.#front.val; // Store tail node value
+        // Delete head node
+        let temp = this.#front.next;
+        if (temp !== null) {
+            temp.prev = null;
+            this.#front.next = null;
+        }
+        this.#front = temp; // Update head node
+        this.#queSize--;
+        return value;
+    }
+
+    /* Driver Code */
+    peekLast() {
+        return this.#queSize === 0 ? null : this.#rear.val;
+    }
+
+    /* Return list for printing */
+    peekFirst() {
+        return this.#queSize === 0 ? null : this.#front.val;
+    }
+
+    /* Get the length of the double-ended queue */
+    size() {
+        return this.#queSize;
+    }
+
+    /* Check if the double-ended queue is empty */
+    isEmpty() {
+        return this.#queSize === 0;
+    }
+
+    /* Print deque */
+    print() {
+        const arr = [];
+        let temp = this.#front;
+        while (temp !== null) {
+            arr.push(temp.val);
+            temp = temp.next;
+        }
+        console.log('[' + arr.join(', ') + ']');
+    }
+}
+
+/* Driver Code */
+/* Get the length of the double-ended queue */
+const linkedListDeque = new LinkedListDeque();
+linkedListDeque.pushLast(3);
+linkedListDeque.pushLast(2);
+linkedListDeque.pushLast(5);
+console.log('Deque linkedListDeque = ');
+linkedListDeque.print();
+
+/* Update element */
+const peekFirst = linkedListDeque.peekFirst();
+console.log('Front element peekFirst = ' + peekFirst);
+const peekLast = linkedListDeque.peekLast();
+console.log('Rear element peekLast = ' + peekLast);
+
+/* Elements enqueue */
+linkedListDeque.pushLast(4);
+console.log('After element 4 enqueues at rear, linkedListDeque = ');
+linkedListDeque.print();
+linkedListDeque.pushFirst(1);
+console.log('After element 1 enqueues at front, linkedListDeque = ');
+linkedListDeque.print();
+
+/* Element dequeue */
+const popLast = linkedListDeque.popLast();
+console.log('Rear dequeue element = ' + popLast + ', after rear dequeue linkedListDeque = ');
+linkedListDeque.print();
+const popFirst = linkedListDeque.popFirst();
+console.log('Front dequeue element = ' + popFirst + ', after front dequeue linkedListDeque = ');
+linkedListDeque.print();
+
+/* Get the length of the double-ended queue */
+const size = linkedListDeque.size();
+console.log('Double-ended queue length size = ' + size);
+
+/* Check if the double-ended queue is empty */
+const isEmpty = linkedListDeque.isEmpty();
+console.log('Double-ended queue is empty = ' + isEmpty);

en/codes/javascript/chapter_stack_and_queue/linkedlist_queue.js

@@ -0,0 +1,99 @@
+/**
+ * File: linkedlist_queue.js
+ * Created Time: 2022-12-20
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+const { ListNode } = require('../modules/ListNode');
+
+/* Queue based on linked list implementation */
+class LinkedListQueue {
+    #front; // Front node #front
+    #rear; // Rear node #rear
+    #queSize = 0;
+
+    constructor() {
+        this.#front = null;
+        this.#rear = null;
+    }
+
+    /* Get the length of the queue */
+    get size() {
+        return this.#queSize;
+    }
+
+    /* Check if the queue is empty */
+    isEmpty() {
+        return this.size === 0;
+    }
+
+    /* Enqueue */
+    push(num) {
+        // Add num after the tail node
+        const node = new ListNode(num);
+        // If the queue is empty, make both front and rear point to the node
+        if (!this.#front) {
+            this.#front = node;
+            this.#rear = node;
+            // If the queue is not empty, add the node after the tail node
+        } else {
+            this.#rear.next = node;
+            this.#rear = node;
+        }
+        this.#queSize++;
+    }
+
+    /* Dequeue */
+    pop() {
+        const num = this.peek();
+        // Delete head node
+        this.#front = this.#front.next;
+        this.#queSize--;
+        return num;
+    }
+
+    /* Return list for printing */
+    peek() {
+        if (this.size === 0) throw new Error('Queue is empty');
+        return this.#front.val;
+    }
+
+    /* Convert linked list to Array and return */
+    toArray() {
+        let node = this.#front;
+        const res = new Array(this.size);
+        for (let i = 0; i < res.length; i++) {
+            res[i] = node.val;
+            node = node.next;
+        }
+        return res;
+    }
+}
+
+/* Driver Code */
+/* Access front of the queue element */
+const queue = new LinkedListQueue();
+
+/* Elements enqueue */
+queue.push(1);
+queue.push(3);
+queue.push(2);
+queue.push(5);
+queue.push(4);
+console.log('Queue queue = ' + queue.toArray());
+
+/* Return list for printing */
+const peek = queue.peek();
+console.log('Front element peek = ' + peek);
+
+/* Element dequeue */
+const pop = queue.pop();
+console.log('Dequeue element pop = ' + pop + ', after dequeue, queue = ' + queue.toArray());
+
+/* Get the length of the queue */
+const size = queue.size;
+console.log('Queue length size = ' + size);
+
+/* Check if the queue is empty */
+const isEmpty = queue.isEmpty();
+console.log('Queue is empty = ' + isEmpty);

en/codes/javascript/chapter_stack_and_queue/linkedlist_stack.js

@@ -0,0 +1,88 @@
+/**
+ * File: linkedlist_stack.js
+ * Created Time: 2022-12-22
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+const { ListNode } = require('../modules/ListNode');
+
+/* Stack based on linked list implementation */
+class LinkedListStack {
+    #stackPeek; // Use head node as stack top
+    #stkSize = 0; // Stack length
+
+    constructor() {
+        this.#stackPeek = null;
+    }
+
+    /* Get the length of the stack */
+    get size() {
+        return this.#stkSize;
+    }
+
+    /* Check if the stack is empty */
+    isEmpty() {
+        return this.size === 0;
+    }
+
+    /* Push */
+    push(num) {
+        const node = new ListNode(num);
+        node.next = this.#stackPeek;
+        this.#stackPeek = node;
+        this.#stkSize++;
+    }
+
+    /* Pop */
+    pop() {
+        const num = this.peek();
+        this.#stackPeek = this.#stackPeek.next;
+        this.#stkSize--;
+        return num;
+    }
+
+    /* Return list for printing */
+    peek() {
+        if (!this.#stackPeek) throw new Error('Stack is empty');
+        return this.#stackPeek.val;
+    }
+
+    /* Convert linked list to Array and return */
+    toArray() {
+        let node = this.#stackPeek;
+        const res = new Array(this.size);
+        for (let i = res.length - 1; i >= 0; i--) {
+            res[i] = node.val;
+            node = node.next;
+        }
+        return res;
+    }
+}
+
+/* Driver Code */
+/* Access top of the stack element */
+const stack = new LinkedListStack();
+
+/* Elements push onto stack */
+stack.push(1);
+stack.push(3);
+stack.push(2);
+stack.push(5);
+stack.push(4);
+console.log('Stack stack = ' + stack.toArray());
+
+/* Return list for printing */
+const peek = stack.peek();
+console.log('Stack top element peek = ' + peek);
+
+/* Element pop from stack */
+const pop = stack.pop();
+console.log('Pop element pop = ' + pop + ', after pop, stack = ' + stack.toArray());
+
+/* Get the length of the stack */
+const size = stack.size;
+console.log('Stack length size = ' + size);
+
+/* Check if empty */
+const isEmpty = stack.isEmpty();
+console.log('Stack is empty = ' + isEmpty);

en/codes/javascript/chapter_stack_and_queue/queue.js

@@ -0,0 +1,35 @@
+/**
+ * File: queue.js
+ * Created Time: 2022-12-05
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+/* Driver Code */
+/* Access front of the queue element */
+// JavaScript has no built-in queue, can use Array as queue
+const queue = [];
+
+/* Elements enqueue */
+queue.push(1);
+queue.push(3);
+queue.push(2);
+queue.push(5);
+queue.push(4);
+console.log('Queue queue =', queue);
+
+/* Return list for printing */
+const peek = queue[0];
+console.log('Front element peek =', peek);
+
+/* Element dequeue */
+// Underlying is array, so shift() method has O(n) time complexity
+const pop = queue.shift();
+console.log('Dequeue element pop =', pop, ', after dequeue, queue = ', queue);
+
+/* Get the length of the queue */
+const size = queue.length;
+console.log('Queue length size =', size);
+
+/* Check if the queue is empty */
+const isEmpty = queue.length === 0;
+console.log('Queue is empty = ', isEmpty);

en/codes/javascript/chapter_stack_and_queue/stack.js

@@ -0,0 +1,35 @@
+/**
+ * File: stack.js
+ * Created Time: 2022-12-04
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+/* Driver Code */
+/* Access top of the stack element */
+// JavaScript has no built-in stack class, can use Array as stack
+const stack = [];
+
+/* Elements push onto stack */
+stack.push(1);
+stack.push(3);
+stack.push(2);
+stack.push(5);
+stack.push(4);
+console.log('Stack stack =', stack);
+
+/* Return list for printing */
+const peek = stack[stack.length - 1];
+console.log('Stack top element peek =', peek);
+
+/* Element pop from stack */
+const pop = stack.pop();
+console.log('Pop element pop =', pop);
+console.log('After pop, stack =', stack);
+
+/* Get the length of the stack */
+const size = stack.length;
+console.log('Stack length size =', size);
+
+/* Check if empty */
+const isEmpty = stack.length === 0;
+console.log('Is stack empty =', isEmpty);

en/codes/javascript/chapter_tree/array_binary_tree.js

@@ -0,0 +1,147 @@
+/**
+ * File: array_binary_tree.js
+ * Created Time: 2023-08-06
+ * Author: yuan0221 (yl1452491917@gmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Binary tree class represented by array */
+class ArrayBinaryTree {
+    #tree;
+
+    /* Constructor */
+    constructor(arr) {
+        this.#tree = arr;
+    }
+
+    /* List capacity */
+    size() {
+        return this.#tree.length;
+    }
+
+    /* Get value of node at index i */
+    val(i) {
+        // If index out of bounds, return null to represent empty position
+        if (i < 0 || i >= this.size()) return null;
+        return this.#tree[i];
+    }
+
+    /* Get index of left child node of node at index i */
+    left(i) {
+        return 2 * i + 1;
+    }
+
+    /* Get index of right child node of node at index i */
+    right(i) {
+        return 2 * i + 2;
+    }
+
+    /* Get index of parent node of node at index i */
+    parent(i) {
+        return Math.floor((i - 1) / 2); // Floor division
+    }
+
+    /* Level-order traversal */
+    levelOrder() {
+        let res = [];
+        // Traverse array directly
+        for (let i = 0; i < this.size(); i++) {
+            if (this.val(i) !== null) res.push(this.val(i));
+        }
+        return res;
+    }
+
+    /* Depth-first traversal */
+    #dfs(i, order, res) {
+        // If empty position, return
+        if (this.val(i) === null) return;
+        // Preorder traversal
+        if (order === 'pre') res.push(this.val(i));
+        this.#dfs(this.left(i), order, res);
+        // Inorder traversal
+        if (order === 'in') res.push(this.val(i));
+        this.#dfs(this.right(i), order, res);
+        // Postorder traversal
+        if (order === 'post') res.push(this.val(i));
+    }
+
+    /* Preorder traversal */
+    preOrder() {
+        const res = [];
+        this.#dfs(0, 'pre', res);
+        return res;
+    }
+
+    /* Inorder traversal */
+    inOrder() {
+        const res = [];
+        this.#dfs(0, 'in', res);
+        return res;
+    }
+
+    /* Postorder traversal */
+    postOrder() {
+        const res = [];
+        this.#dfs(0, 'post', res);
+        return res;
+    }
+}
+
+/* Driver Code */
+// Initialize binary tree
+// Here we use a function to generate a binary tree directly from an array
+const arr = Array.of(
+    1,
+    2,
+    3,
+    4,
+    null,
+    6,
+    7,
+    8,
+    9,
+    null,
+    null,
+    12,
+    null,
+    null,
+    15
+);
+
+const root = arrToTree(arr);
+console.log('\nInitialize binary tree\n');
+console.log('Array representation of binary tree:');
+console.log(arr);
+console.log('Linked list representation of binary tree:');
+printTree(root);
+
+// Binary tree class represented by array
+const abt = new ArrayBinaryTree(arr);
+
+// Access node
+const i = 1;
+const l = abt.left(i);
+const r = abt.right(i);
+const p = abt.parent(i);
+console.log('\nCurrent node index is ' + i + ', value is ' + abt.val(i));
+console.log(
+    'Its left child node index is ' + l + ', value is ' + (l === null ? 'null' : abt.val(l))
+);
+console.log(
+    'Its right child node index is ' + r + ', value is ' + (r === null ? 'null' : abt.val(r))
+);
+console.log(
+    'Its parent node index is ' + p + ', value is ' + (p === null ? 'null' : abt.val(p))
+);
+
+// Traverse tree
+let res = abt.levelOrder();
+console.log('\nLevel-order traversal is:' + res);
+res = abt.preOrder();
+console.log('Preorder traversal is:' + res);
+res = abt.inOrder();
+console.log('Inorder traversal is:' + res);
+res = abt.postOrder();
+console.log('Postorder traversal is:' + res);

en/codes/javascript/chapter_tree/avl_tree.js

@@ -0,0 +1,208 @@
+/**
+ * File: avl_tree.js
+ * Created Time: 2023-02-05
+ * Author: what-is-me (whatisme@outlook.jp)
+ */
+
+const { TreeNode } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* AVL tree */
+class AVLTree {
+    /* Constructor */
+    constructor() {
+        this.root = null; // Root node
+    }
+
+    /* Get node height */
+    height(node) {
+        // Empty node height is -1, leaf node height is 0
+        return node === null ? -1 : node.height;
+    }
+
+    /* Update node height */
+    #updateHeight(node) {
+        // Node height equals the height of the tallest subtree + 1
+        node.height =
+            Math.max(this.height(node.left), this.height(node.right)) + 1;
+    }
+
+    /* Get balance factor */
+    balanceFactor(node) {
+        // Empty node balance factor is 0
+        if (node === null) return 0;
+        // Node balance factor = left subtree height - right subtree height
+        return this.height(node.left) - this.height(node.right);
+    }
+
+    /* Right rotation operation */
+    #rightRotate(node) {
+        const child = node.left;
+        const grandChild = child.right;
+        // Using child as pivot, rotate node to the right
+        child.right = node;
+        node.left = grandChild;
+        // Update node height
+        this.#updateHeight(node);
+        this.#updateHeight(child);
+        // Return root node of subtree after rotation
+        return child;
+    }
+
+    /* Left rotation operation */
+    #leftRotate(node) {
+        const child = node.right;
+        const grandChild = child.left;
+        // Using child as pivot, rotate node to the left
+        child.left = node;
+        node.right = grandChild;
+        // Update node height
+        this.#updateHeight(node);
+        this.#updateHeight(child);
+        // Return root node of subtree after rotation
+        return child;
+    }
+
+    /* Perform rotation operation to restore balance to this subtree */
+    #rotate(node) {
+        // Get balance factor of node
+        const balanceFactor = this.balanceFactor(node);
+        // Left-leaning tree
+        if (balanceFactor > 1) {
+            if (this.balanceFactor(node.left) >= 0) {
+                // Right rotation
+                return this.#rightRotate(node);
+            } else {
+                // First left rotation then right rotation
+                node.left = this.#leftRotate(node.left);
+                return this.#rightRotate(node);
+            }
+        }
+        // Right-leaning tree
+        if (balanceFactor < -1) {
+            if (this.balanceFactor(node.right) <= 0) {
+                // Left rotation
+                return this.#leftRotate(node);
+            } else {
+                // First right rotation then left rotation
+                node.right = this.#rightRotate(node.right);
+                return this.#leftRotate(node);
+            }
+        }
+        // Balanced tree, no rotation needed, return directly
+        return node;
+    }
+
+    /* Insert node */
+    insert(val) {
+        this.root = this.#insertHelper(this.root, val);
+    }
+
+    /* Recursively insert node (helper method) */
+    #insertHelper(node, val) {
+        if (node === null) return new TreeNode(val);
+        /* 1. Find insertion position and insert node */
+        if (val < node.val) node.left = this.#insertHelper(node.left, val);
+        else if (val > node.val)
+            node.right = this.#insertHelper(node.right, val);
+        else return node; // Duplicate node not inserted, return directly
+        this.#updateHeight(node); // Update node height
+        /* 2. Perform rotation operation to restore balance to this subtree */
+        node = this.#rotate(node);
+        // Return root node of subtree
+        return node;
+    }
+
+    /* Remove node */
+    remove(val) {
+        this.root = this.#removeHelper(this.root, val);
+    }
+
+    /* Recursively delete node (helper method) */
+    #removeHelper(node, val) {
+        if (node === null) return null;
+        /* 1. Find node and delete */
+        if (val < node.val) node.left = this.#removeHelper(node.left, val);
+        else if (val > node.val)
+            node.right = this.#removeHelper(node.right, val);
+        else {
+            if (node.left === null || node.right === null) {
+                const child = node.left !== null ? node.left : node.right;
+                // Number of child nodes = 0, delete node directly and return
+                if (child === null) return null;
+                // Number of child nodes = 1, delete node directly
+                else node = child;
+            } else {
+                // Number of child nodes = 2, delete the next node in inorder traversal and replace current node with it
+                let temp = node.right;
+                while (temp.left !== null) {
+                    temp = temp.left;
+                }
+                node.right = this.#removeHelper(node.right, temp.val);
+                node.val = temp.val;
+            }
+        }
+        this.#updateHeight(node); // Update node height
+        /* 2. Perform rotation operation to restore balance to this subtree */
+        node = this.#rotate(node);
+        // Return root node of subtree
+        return node;
+    }
+
+    /* Search node */
+    search(val) {
+        let cur = this.root;
+        // Loop search, exit after passing leaf node
+        while (cur !== null) {
+            // Target node is in cur's right subtree
+            if (cur.val < val) cur = cur.right;
+            // Target node is in cur's left subtree
+            else if (cur.val > val) cur = cur.left;
+            // Found target node, exit loop
+            else break;
+        }
+        // Return target node
+        return cur;
+    }
+}
+
+function testInsert(tree, val) {
+    tree.insert(val);
+    console.log('\nInsert node ' + val + ', AVL tree is');
+    printTree(tree.root);
+}
+
+function testRemove(tree, val) {
+    tree.remove(val);
+    console.log('\nRemove node ' + val + ', AVL tree is');
+    printTree(tree.root);
+}
+
+/* Driver Code */
+/* Please pay attention to how the AVL tree maintains balance after inserting nodes */
+const avlTree = new AVLTree();
+/* Insert node */
+// Delete nodes
+testInsert(avlTree, 1);
+testInsert(avlTree, 2);
+testInsert(avlTree, 3);
+testInsert(avlTree, 4);
+testInsert(avlTree, 5);
+testInsert(avlTree, 8);
+testInsert(avlTree, 7);
+testInsert(avlTree, 9);
+testInsert(avlTree, 10);
+testInsert(avlTree, 6);
+
+/* Please pay attention to how the AVL tree maintains balance after deleting nodes */
+testInsert(avlTree, 7);
+
+/* Remove node */
+// Delete node with degree 1
+testRemove(avlTree, 8); // Delete node with degree 2
+testRemove(avlTree, 5); // Remove node with degree 1
+testRemove(avlTree, 4); // Remove node with degree 2
+
+/* Search node */
+const node = avlTree.search(7);
+console.log('\nFound node object is', node, ', node value = ' + node.val);

en/codes/javascript/chapter_tree/binary_search_tree.js

@@ -0,0 +1,139 @@
+/**
+ * File: binary_search_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { TreeNode } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Binary search tree */
+class BinarySearchTree {
+    /* Constructor */
+    constructor() {
+        // Initialize empty tree
+        this.root = null;
+    }
+
+    /* Get binary tree root node */
+    getRoot() {
+        return this.root;
+    }
+
+    /* Search node */
+    search(num) {
+        let cur = this.root;
+        // Loop search, exit after passing leaf node
+        while (cur !== null) {
+            // Target node is in cur's right subtree
+            if (cur.val < num) cur = cur.right;
+            // Target node is in cur's left subtree
+            else if (cur.val > num) cur = cur.left;
+            // Found target node, exit loop
+            else break;
+        }
+        // Return target node
+        return cur;
+    }
+
+    /* Insert node */
+    insert(num) {
+        // If tree is empty, initialize root node
+        if (this.root === null) {
+            this.root = new TreeNode(num);
+            return;
+        }
+        let cur = this.root,
+            pre = null;
+        // Loop search, exit after passing leaf node
+        while (cur !== null) {
+            // Found duplicate node, return directly
+            if (cur.val === num) return;
+            pre = cur;
+            // Insertion position is in cur's right subtree
+            if (cur.val < num) cur = cur.right;
+            // Insertion position is in cur's left subtree
+            else cur = cur.left;
+        }
+        // Insert node
+        const node = new TreeNode(num);
+        if (pre.val < num) pre.right = node;
+        else pre.left = node;
+    }
+
+    /* Remove node */
+    remove(num) {
+        // If tree is empty, return directly
+        if (this.root === null) return;
+        let cur = this.root,
+            pre = null;
+        // Loop search, exit after passing leaf node
+        while (cur !== null) {
+            // Found node to delete, exit loop
+            if (cur.val === num) break;
+            pre = cur;
+            // Node to delete is in cur's right subtree
+            if (cur.val < num) cur = cur.right;
+            // Node to delete is in cur's left subtree
+            else cur = cur.left;
+        }
+        // If no node to delete, return directly
+        if (cur === null) return;
+        // Number of child nodes = 0 or 1
+        if (cur.left === null || cur.right === null) {
+            // When number of child nodes = 0 / 1, child = null / that child node
+            const child = cur.left !== null ? cur.left : cur.right;
+            // Delete node cur
+            if (cur !== this.root) {
+                if (pre.left === cur) pre.left = child;
+                else pre.right = child;
+            } else {
+                // If deleted node is root node, reassign root node
+                this.root = child;
+            }
+        }
+        // Number of child nodes = 2
+        else {
+            // Get next node of cur in inorder traversal
+            let tmp = cur.right;
+            while (tmp.left !== null) {
+                tmp = tmp.left;
+            }
+            // Recursively delete node tmp
+            this.remove(tmp.val);
+            // Replace cur with tmp
+            cur.val = tmp.val;
+        }
+    }
+}
+
+/* Driver Code */
+/* Initialize binary search tree */
+const bst = new BinarySearchTree();
+// Please note that different insertion orders will generate different binary trees, this sequence can generate a perfect binary tree
+const nums = [8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15];
+for (const num of nums) {
+    bst.insert(num);
+}
+console.log('\nInitialized binary tree is\n');
+printTree(bst.getRoot());
+
+/* Search node */
+const node = bst.search(7);
+console.log('\nFound node object is ' + node + ', node value = ' + node.val);
+
+/* Insert node */
+bst.insert(16);
+console.log('\nAfter inserting node 16, binary tree is\n');
+printTree(bst.getRoot());
+
+/* Remove node */
+bst.remove(1);
+console.log('\nAfter removing node 1, binary tree is\n');
+printTree(bst.getRoot());
+bst.remove(2);
+console.log('\nAfter removing node 2, binary tree is\n');
+printTree(bst.getRoot());
+bst.remove(4);
+console.log('\nAfter removing node 4, binary tree is\n');
+printTree(bst.getRoot());

en/codes/javascript/chapter_tree/binary_tree.js

@@ -0,0 +1,35 @@
+/**
+ * File: binary_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { TreeNode } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Initialize binary tree */
+// Initialize nodes
+let n1 = new TreeNode(1),
+    n2 = new TreeNode(2),
+    n3 = new TreeNode(3),
+    n4 = new TreeNode(4),
+    n5 = new TreeNode(5);
+// Build references (pointers) between nodes
+n1.left = n2;
+n1.right = n3;
+n2.left = n4;
+n2.right = n5;
+console.log('\nInitialize binary tree\n');
+printTree(n1);
+
+/* Insert node P between n1 -> n2 */
+const P = new TreeNode(0);
+// Delete node
+n1.left = P;
+P.left = n2;
+console.log('\nAfter inserting node P\n');
+printTree(n1);
+// Remove node P
+n1.left = n2;
+console.log('\nAfter removing node P\n');
+printTree(n1);

en/codes/javascript/chapter_tree/binary_tree_bfs.js

@@ -0,0 +1,34 @@
+/**
+ * File: binary_tree_bfs.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+/* Level-order traversal */
+function levelOrder(root) {
+    // Initialize queue, add root node
+    const queue = [root];
+    // Initialize a list to save the traversal sequence
+    const list = [];
+    while (queue.length) {
+        let node = queue.shift(); // Dequeue
+        list.push(node.val); // Save node value
+        if (node.left) queue.push(node.left); // Left child node enqueue
+        if (node.right) queue.push(node.right); // Right child node enqueue
+    }
+    return list;
+}
+
+/* Driver Code */
+/* Initialize binary tree */
+// Here we use a function to generate a binary tree directly from an array
+const root = arrToTree([1, 2, 3, 4, 5, 6, 7]);
+console.log('\nInitialize binary tree\n');
+printTree(root);
+
+/* Level-order traversal */
+const list = levelOrder(root);
+console.log('\nLevel-order traversal node print sequence = ' + list);

en/codes/javascript/chapter_tree/binary_tree_dfs.js

@@ -0,0 +1,60 @@
+/**
+ * File: binary_tree_dfs.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { arrToTree } = require('../modules/TreeNode');
+const { printTree } = require('../modules/PrintUtil');
+
+// Initialize list for storing traversal sequence
+const list = [];
+
+/* Preorder traversal */
+function preOrder(root) {
+    if (root === null) return;
+    // Visit priority: root node -> left subtree -> right subtree
+    list.push(root.val);
+    preOrder(root.left);
+    preOrder(root.right);
+}
+
+/* Inorder traversal */
+function inOrder(root) {
+    if (root === null) return;
+    // Visit priority: left subtree -> root node -> right subtree
+    inOrder(root.left);
+    list.push(root.val);
+    inOrder(root.right);
+}
+
+/* Postorder traversal */
+function postOrder(root) {
+    if (root === null) return;
+    // Visit priority: left subtree -> right subtree -> root node
+    postOrder(root.left);
+    postOrder(root.right);
+    list.push(root.val);
+}
+
+/* Driver Code */
+/* Initialize binary tree */
+// Here we use a function to generate a binary tree directly from an array
+const root = arrToTree([1, 2, 3, 4, 5, 6, 7]);
+console.log('\nInitialize binary tree\n');
+printTree(root);
+
+/* Preorder traversal */
+list.length = 0;
+preOrder(root);
+console.log('\nPreorder traversal node print sequence = ' + list);
+
+/* Inorder traversal */
+list.length = 0;
+inOrder(root);
+console.log('\nInorder traversal node print sequence = ' + list);
+
+/* Postorder traversal */
+list.length = 0;
+postOrder(root);
+console.log('\nPostorder traversal node print sequence = ' + list);

en/codes/javascript/modules/ListNode.js

@@ -0,0 +1,31 @@
+/**
+ * File: ListNode.js
+ * Created Time: 2022-12-12
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Linked list node */
+class ListNode {
+    val; // Node value
+    next; // Reference (pointer) to next node
+    constructor(val, next) {
+        this.val = val === undefined ? 0 : val;
+        this.next = next === undefined ? null : next;
+    }
+}
+
+/* Deserialize a list into a linked list */
+function arrToLinkedList(arr) {
+    const dum = new ListNode(0);
+    let head = dum;
+    for (const val of arr) {
+        head.next = new ListNode(val);
+        head = head.next;
+    }
+    return dum.next;
+}
+
+module.exports = {
+    ListNode,
+    arrToLinkedList,
+};

en/codes/javascript/modules/PrintUtil.js

@@ -0,0 +1,86 @@
+/**
+ * File: PrintUtil.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+const { arrToTree } = require('./TreeNode');
+
+/* Print linked list */
+function printLinkedList(head) {
+    let list = [];
+    while (head !== null) {
+        list.push(head.val.toString());
+        head = head.next;
+    }
+    console.log(list.join(' -> '));
+}
+
+function Trunk(prev, str) {
+    this.prev = prev;
+    this.str = str;
+}
+
+/**
+ * Print binary tree
+ * This tree printer is borrowed from TECHIE DELIGHT
+ * https://www.techiedelight.com/c-program-print-binary-tree/
+ */
+function printTree(root) {
+    printTree(root, null, false);
+}
+
+/* Print binary tree */
+function printTree(root, prev, isRight) {
+    if (root === null) {
+        return;
+    }
+
+    let prev_str = '    ';
+    let trunk = new Trunk(prev, prev_str);
+
+    printTree(root.right, trunk, true);
+
+    if (!prev) {
+        trunk.str = '———';
+    } else if (isRight) {
+        trunk.str = '/———';
+        prev_str = '   |';
+    } else {
+        trunk.str = '\\———';
+        prev.str = prev_str;
+    }
+
+    showTrunks(trunk);
+    console.log(' ' + root.val);
+
+    if (prev) {
+        prev.str = prev_str;
+    }
+    trunk.str = '   |';
+
+    printTree(root.left, trunk, false);
+}
+
+function showTrunks(p) {
+    if (!p) {
+        return;
+    }
+
+    showTrunks(p.prev);
+    process.stdout.write(p.str);
+}
+
+/* Print heap */
+function printHeap(arr) {
+    console.log('Heap array representation:');
+    console.log(arr);
+    console.log('Heap tree representation:');
+    printTree(arrToTree(arr));
+}
+
+module.exports = {
+    printLinkedList,
+    printTree,
+    printHeap,
+};

en/codes/javascript/modules/TreeNode.js

@@ -0,0 +1,35 @@
+/**
+ * File: TreeNode.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+/* Binary tree node */
+class TreeNode {
+    val; // Node value
+    left; // Left child pointer
+    right; // Right child pointer
+    height; // Node height
+    constructor(val, left, right, height) {
+        this.val = val === undefined ? 0 : val;
+        this.left = left === undefined ? null : left;
+        this.right = right === undefined ? null : right;
+        this.height = height === undefined ? 0 : height;
+    }
+}
+
+/* Deserialize array to binary tree */
+function arrToTree(arr, i = 0) {
+    if (i < 0 || i >= arr.length || arr[i] === null) {
+        return null;
+    }
+    let root = new TreeNode(arr[i]);
+    root.left = arrToTree(arr, 2 * i + 1);
+    root.right = arrToTree(arr, 2 * i + 2);
+    return root;
+}
+
+module.exports = {
+    TreeNode,
+    arrToTree,
+};

en/codes/javascript/modules/Vertex.js

@@ -0,0 +1,35 @@
+/**
+ * File: Vertex.js
+ * Created Time: 2023-02-15
+ * Author: Zhuo Qinyue (1403450829@qq.com)
+ */
+
+/* Vertex class */
+class Vertex {
+    val;
+    constructor(val) {
+        this.val = val;
+    }
+
+    /* Input value list vals, return vertex list vets */
+    static valsToVets(vals) {
+        const vets = [];
+        for (let i = 0; i < vals.length; i++) {
+            vets[i] = new Vertex(vals[i]);
+        }
+        return vets;
+    }
+
+    /* Input vertex list vets, return value list vals */
+    static vetsToVals(vets) {
+        const vals = [];
+        for (const vet of vets) {
+            vals.push(vet.val);
+        }
+        return vals;
+    }
+}
+
+module.exports = {
+    Vertex,
+};

en/codes/javascript/test_all.js

@@ -0,0 +1,63 @@
+import { bold, brightRed } from 'jsr:@std/fmt/colors';
+import { expandGlob } from 'jsr:@std/fs';
+import { relative, resolve } from 'jsr:@std/path';
+
+/**
+ * @typedef {import('jsr:@std/fs').WalkEntry} WalkEntry
+ * @type {WalkEntry[]}
+ */
+const entries = [];
+
+for await (const entry of expandGlob(
+    resolve(import.meta.dirname, './chapter_*/*.js')
+)) {
+    entries.push(entry);
+}
+
+/** @type {{ status: Promise<Deno.CommandStatus>; stderr: ReadableStream<Uint8Array>; }[]} */
+const processes = [];
+
+for (const file of entries) {
+    const execute = new Deno.Command('node', {
+        args: [relative(import.meta.dirname, file.path)],
+        cwd: import.meta.dirname,
+        stdin: 'piped',
+        stdout: 'piped',
+        stderr: 'piped',
+    });
+
+    const process = execute.spawn();
+    processes.push({ status: process.status, stderr: process.stderr });
+}
+
+const results = await Promise.all(
+    processes.map(async (item) => {
+        const status = await item.status;
+        return { status, stderr: item.stderr };
+    })
+);
+
+/** @type {ReadableStream<Uint8Array>[]} */
+const errors = [];
+
+for (const result of results) {
+    if (!result.status.success) {
+        errors.push(result.stderr);
+    }
+}
+
+console.log(`Tested ${entries.length} files`);
+console.log(`Found exception in ${errors.length} files`);
+
+if (errors.length) {
+    console.log();
+
+    for (const error of errors) {
+        const reader = error.getReader();
+        const { value } = await reader.read();
+        const decoder = new TextDecoder();
+        console.log(`${bold(brightRed('error'))}: ${decoder.decode(value)}`);
+    }
+
+    throw new Error('Test failed');
+}