Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_sorting/CMakeLists.txt

@@ -0,0 +1,6 @@
+add_executable(selection_sort selection_sort.cpp)
+add_executable(bubble_sort bubble_sort.cpp)
+add_executable(insertion_sort insertion_sort.cpp)
+add_executable(merge_sort merge_sort.cpp)
+add_executable(quick_sort quick_sort.cpp)
+add_executable(heap_sort heap_sort.cpp)

en/codes/cpp/chapter_sorting/bubble_sort.cpp

@@ -0,0 +1,56 @@
+/**
+ * File: bubble_sort.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Bubble sort */
+void bubbleSort(vector<int> &nums) {
+    // Outer loop: unsorted range is [0, i]
+    for (int i = nums.size() - 1; i > 0; i--) {
+        // Inner loop: swap the largest element in the unsorted range [0, i] to the right end of the range
+        for (int j = 0; j < i; j++) {
+            if (nums[j] > nums[j + 1]) {
+                // Swap nums[j] and nums[j + 1]
+                // Here, the std
+                swap(nums[j], nums[j + 1]);
+            }
+        }
+    }
+}
+
+/* Bubble sort (optimized with flag)*/
+void bubbleSortWithFlag(vector<int> &nums) {
+    // Outer loop: unsorted range is [0, i]
+    for (int i = nums.size() - 1; i > 0; i--) {
+        bool flag = false; // Initialize flag
+        // Inner loop: swap the largest element in the unsorted range [0, i] to the right end of the range
+        for (int j = 0; j < i; j++) {
+            if (nums[j] > nums[j + 1]) {
+                // Swap nums[j] and nums[j + 1]
+                // Here, the std
+                swap(nums[j], nums[j + 1]);
+                flag = true; // Record swapped elements
+            }
+        }
+        if (!flag)
+            break; // If no elements were swapped in this round of "bubbling", exit
+    }
+}
+
+/* Driver Code */
+int main() {
+    vector<int> nums = {4, 1, 3, 1, 5, 2};
+    bubbleSort(nums);
+    cout << "After bubble sort, nums = ";
+    printVector(nums);
+
+    vector<int> nums1 = {4, 1, 3, 1, 5, 2};
+    bubbleSortWithFlag(nums1);
+    cout << "After bubble sort, nums1 = ";
+    printVector(nums1);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/bucket_sort.cpp

@@ -0,0 +1,44 @@
+/**
+ * File: bucket_sort.cpp
+ * Created Time: 2023-03-30
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Bucket sort */
+void bucketSort(vector<float> &nums) {
+    // Initialize k = n/2 buckets, expected to allocate 2 elements per bucket
+    int k = nums.size() / 2;
+    vector<vector<float>> buckets(k);
+    // 1. Distribute array elements into various buckets
+    for (float num : nums) {
+        // Input data range is [0, 1), use num * k to map to index range [0, k-1]
+        int i = num * k;
+        // Add number to bucket_idx
+        buckets[i].push_back(num);
+    }
+    // 2. Sort each bucket
+    for (vector<float> &bucket : buckets) {
+        // Use built-in sorting function, can also replace with other sorting algorithms
+        sort(bucket.begin(), bucket.end());
+    }
+    // 3. Traverse buckets to merge results
+    int i = 0;
+    for (vector<float> &bucket : buckets) {
+        for (float num : bucket) {
+            nums[i++] = num;
+        }
+    }
+}
+
+/* Driver Code */
+int main() {
+    // Assume input data is floating point, range [0, 1)
+    vector<float> nums = {0.49f, 0.96f, 0.82f, 0.09f, 0.57f, 0.43f, 0.91f, 0.75f, 0.15f, 0.37f};
+    bucketSort(nums);
+    cout << "After bucket sort, nums = ";
+    printVector(nums);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/counting_sort.cpp

@@ -0,0 +1,77 @@
+/**
+ * File: counting_sort.cpp
+ * Created Time: 2023-03-17
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Counting sort */
+// Simple implementation, cannot be used for sorting objects
+void countingSortNaive(vector<int> &nums) {
+    // 1. Count the maximum element m in the array
+    int m = 0;
+    for (int num : nums) {
+        m = max(m, num);
+    }
+    // 2. Count the occurrence of each digit
+    // counter[num] represents the occurrence of num
+    vector<int> counter(m + 1, 0);
+    for (int num : nums) {
+        counter[num]++;
+    }
+    // 3. Traverse counter, filling each element back into the original array nums
+    int i = 0;
+    for (int num = 0; num < m + 1; num++) {
+        for (int j = 0; j < counter[num]; j++, i++) {
+            nums[i] = num;
+        }
+    }
+}
+
+/* Counting sort */
+// Complete implementation, can sort objects and is a stable sort
+void countingSort(vector<int> &nums) {
+    // 1. Count the maximum element m in the array
+    int m = 0;
+    for (int num : nums) {
+        m = max(m, num);
+    }
+    // 2. Count the occurrence of each digit
+    // counter[num] represents the occurrence of num
+    vector<int> counter(m + 1, 0);
+    for (int num : 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 (int 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
+    int n = nums.size();
+    vector<int> res(n);
+    for (int i = n - 1; i >= 0; i--) {
+        int 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
+    nums = res;
+}
+
+/* Driver Code */
+int main() {
+    vector<int> nums = {1, 0, 1, 2, 0, 4, 0, 2, 2, 4};
+    countingSortNaive(nums);
+    cout << "After count sort (unable to sort objects), nums = ";
+    printVector(nums);
+
+    vector<int> nums1 = {1, 0, 1, 2, 0, 4, 0, 2, 2, 4};
+    countingSort(nums1);
+    cout << "After count sort, nums1 = ";
+    printVector(nums1);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/heap_sort.cpp

@@ -0,0 +1,54 @@
+/**
+ * File: heap_sort.cpp
+ * Created Time: 2023-05-26
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Heap length is n, start heapifying node i, from top to bottom */
+void siftDown(vector<int> &nums, int n, int i) {
+    while (true) {
+        // Determine the largest node among i, l, r, noted as ma
+        int l = 2 * i + 1;
+        int r = 2 * i + 2;
+        int ma = i;
+        if (l < n && nums[l] > nums[ma])
+            ma = l;
+        if (r < n && nums[r] > nums[ma])
+            ma = r;
+        // If node i is the largest or indices l, r are out of bounds, no further heapification needed, break
+        if (ma == i) {
+            break;
+        }
+        // Swap two nodes
+        swap(nums[i], nums[ma]);
+        // Loop downwards heapification
+        i = ma;
+    }
+}
+
+/* Heap sort */
+void heapSort(vector<int> &nums) {
+    // Build heap operation: heapify all nodes except leaves
+    for (int i = nums.size() / 2 - 1; i >= 0; --i) {
+        siftDown(nums, nums.size(), i);
+    }
+    // Extract the largest element from the heap and repeat for n-1 rounds
+    for (int i = nums.size() - 1; i > 0; --i) {
+        // Swap the root node with the rightmost leaf node (swap the first element with the last element)
+        swap(nums[0], nums[i]);
+        // Start heapifying the root node, from top to bottom
+        siftDown(nums, i, 0);
+    }
+}
+
+/* Driver Code */
+int main() {
+    vector<int> nums = {4, 1, 3, 1, 5, 2};
+    heapSort(nums);
+    cout << "After heap sort, nums = ";
+    printVector(nums);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/insertion_sort.cpp

@@ -0,0 +1,31 @@
+/**
+ * File: insertion_sort.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Insertion sort */
+void insertionSort(vector<int> &nums) {
+    // Outer loop: sorted range is [0, i-1]
+    for (int i = 1; i < nums.size(); i++) {
+        int base = nums[i], j = i - 1;
+        // Inner loop: insert base into the correct position within the sorted range [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 */
+int main() {
+    vector<int> nums = {4, 1, 3, 1, 5, 2};
+    insertionSort(nums);
+    cout << "After insertion sort, nums = ";
+    printVector(nums);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/merge_sort.cpp

@@ -0,0 +1,58 @@
+/**
+ * File: merge_sort.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Merge left subarray and right subarray */
+void merge(vector<int> &nums, int left, int mid, int right) {
+    // Left subarray interval is [left, mid], right subarray interval is [mid+1, right]
+    // Create a temporary array tmp to store the merged results
+    vector<int> tmp(right - left + 1);
+    // Initialize the start indices of the left and right subarrays
+    int 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.size(); k++) {
+        nums[left + k] = tmp[k];
+    }
+}
+
+/* Merge sort */
+void mergeSort(vector<int> &nums, int left, int right) {
+    // Termination condition
+    if (left >= right)
+        return; // Terminate recursion when subarray length is 1
+    // Partition stage
+    int mid = (left + right) / 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 */
+int main() {
+    /* Merge sort */
+    vector<int> nums = {7, 3, 2, 6, 0, 1, 5, 4};
+    mergeSort(nums, 0, nums.size() - 1);
+    cout << "After merge sort, nums = ";
+    printVector(nums);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/quick_sort.cpp

@@ -0,0 +1,166 @@
+/**
+ * File: quick_sort.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Quick sort class */
+class QuickSort {
+  private:
+    /* Swap elements */
+    static void swap(vector<int> &nums, int i, int j) {
+        int tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+    }
+
+    /* Partition */
+    static int partition(vector<int> &nums, int left, int right) {
+        // Use nums[left] as the pivot
+        int 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
+            swap(nums, i, j); // Swap these two elements
+        }
+        swap(nums, i, left); // Swap the pivot to the boundary between the two subarrays
+        return i;            // Return the index of the pivot
+    }
+
+  public:
+    /* Quick sort */
+    static void quickSort(vector<int> &nums, int left, int right) {
+        // Terminate recursion when subarray length is 1
+        if (left >= right)
+            return;
+        // Partition
+        int pivot = partition(nums, left, right);
+        // Recursively process the left subarray and right subarray
+        quickSort(nums, left, pivot - 1);
+        quickSort(nums, pivot + 1, right);
+    }
+};
+
+/* Quick sort class (median pivot optimization) */
+class QuickSortMedian {
+  private:
+    /* Swap elements */
+    static void swap(vector<int> &nums, int i, int j) {
+        int tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+    }
+
+    /* Select the median of three candidate elements */
+    static int medianThree(vector<int> &nums, int left, int mid, int right) {
+        int l = nums[left], m = nums[mid], r = nums[right];
+        if ((l <= m && m <= r) || (r <= m && m <= l))
+            return mid; // m is between l and r
+        if ((m <= l && l <= r) || (r <= l && l <= m))
+            return left; // l is between m and r
+        return right;
+    }
+
+    /* Partition (median of three) */
+    static int partition(vector<int> &nums, int left, int right) {
+        // Select the median of three candidate elements
+        int med = medianThree(nums, left, (left + right) / 2, right);
+        // Swap the median to the array's leftmost position
+        swap(nums, left, med);
+        // Use nums[left] as the pivot
+        int 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
+            swap(nums, i, j); // Swap these two elements
+        }
+        swap(nums, i, left); // Swap the pivot to the boundary between the two subarrays
+        return i;            // Return the index of the pivot
+    }
+
+  public:
+    /* Quick sort */
+    static void quickSort(vector<int> &nums, int left, int right) {
+        // Terminate recursion when subarray length is 1
+        if (left >= right)
+            return;
+        // Partition
+        int pivot = partition(nums, left, right);
+        // Recursively process the left subarray and right subarray
+        quickSort(nums, left, pivot - 1);
+        quickSort(nums, pivot + 1, right);
+    }
+};
+
+/* Quick sort class (tail recursion optimization) */
+class QuickSortTailCall {
+  private:
+    /* Swap elements */
+    static void swap(vector<int> &nums, int i, int j) {
+        int tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+    }
+
+    /* Partition */
+    static int partition(vector<int> &nums, int left, int right) {
+        // Use nums[left] as the pivot
+        int 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
+            swap(nums, i, j); // Swap these two elements
+        }
+        swap(nums, i, left); // Swap the pivot to the boundary between the two subarrays
+        return i;            // Return the index of the pivot
+    }
+
+  public:
+    /* Quick sort (tail recursion optimization) */
+    static void quickSort(vector<int> &nums, int left, int right) {
+        // Terminate when subarray length is 1
+        while (left < right) {
+            // Partition operation
+            int pivot = partition(nums, left, right);
+            // Perform quick sort on the shorter of the two subarrays
+            if (pivot - left < right - pivot) {
+                quickSort(nums, left, pivot - 1); // Recursively sort the left subarray
+                left = pivot + 1;                 // Remaining unsorted interval is [pivot + 1, right]
+            } else {
+                quickSort(nums, pivot + 1, right); // Recursively sort the right subarray
+                right = pivot - 1;                 // Remaining unsorted interval is [left, pivot - 1]
+            }
+        }
+    }
+};
+
+/* Driver Code */
+int main() {
+    /* Quick sort */
+    vector<int> nums{2, 4, 1, 0, 3, 5};
+    QuickSort::quickSort(nums, 0, nums.size() - 1);
+    cout << "After quick sort, nums = ";
+    printVector(nums);
+
+    /* Quick sort (median pivot optimization) */
+    vector<int> nums1 = {2, 4, 1, 0, 3, 5};
+    QuickSortMedian::quickSort(nums1, 0, nums1.size() - 1);
+    cout << "Quick sort (median pivot optimization) completed, nums = ";
+    printVector(nums1);
+
+    /* Quick sort (tail recursion optimization) */
+    vector<int> nums2 = {2, 4, 1, 0, 3, 5};
+    QuickSortTailCall::quickSort(nums2, 0, nums2.size() - 1);
+    cout << "Quick sort (tail recursion optimization) completed, nums = ";
+    printVector(nums2);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/radix_sort.cpp

@@ -0,0 +1,65 @@
+/**
+ * File: radix_sort.cpp
+ * Created Time: 2023-03-26
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Get the k-th digit of element num, where exp = 10^(k-1) */
+int digit(int num, int exp) {
+    // Passing exp instead of k can avoid repeated expensive exponentiation here
+    return (num / exp) % 10;
+}
+
+/* Counting sort (based on nums k-th digit) */
+void countingSortDigit(vector<int> &nums, int exp) {
+    // Decimal digit range is 0~9, therefore need a bucket array of length 10
+    vector<int> counter(10, 0);
+    int n = nums.size();
+    // Count the occurrence of digits 0~9
+    for (int i = 0; i < n; i++) {
+        int 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 (int i = 1; i < 10; i++) {
+        counter[i] += counter[i - 1];
+    }
+    // Traverse in reverse, based on bucket statistics, place each element into res
+    vector<int> res(n, 0);
+    for (int i = n - 1; i >= 0; i--) {
+        int d = digit(nums[i], exp);
+        int 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 (int i = 0; i < n; i++)
+        nums[i] = res[i];
+}
+
+/* Radix sort */
+void radixSort(vector<int> &nums) {
+    // Get the maximum element of the array, used to determine the maximum number of digits
+    int m = *max_element(nums.begin(), nums.end());
+    // Traverse from the lowest to the highest digit
+    for (int 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 */
+int main() {
+    // Radix sort
+    vector<int> nums = {10546151, 35663510, 42865989, 34862445, 81883077,
+                        88906420, 72429244, 30524779, 82060337, 63832996};
+    radixSort(nums);
+    cout << "After radix sort, nums = ";
+    printVector(nums);
+
+    return 0;
+}

en/codes/cpp/chapter_sorting/selection_sort.cpp

@@ -0,0 +1,34 @@
+/**
+ * File: selection_sort.cpp
+ * Created Time: 2023-05-23
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Selection sort */
+void selectionSort(vector<int> &nums) {
+    int n = nums.size();
+    // Outer loop: unsorted range is [i, n-1]
+    for (int i = 0; i < n - 1; i++) {
+        // Inner loop: find the smallest element within the unsorted range
+        int k = i;
+        for (int 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 range
+        swap(nums[i], nums[k]);
+    }
+}
+
+/* Driver Code */
+int main() {
+    vector<int> nums = {4, 1, 3, 1, 5, 2};
+    selectionSort(nums);
+
+    cout << "After selection sort, nums = ";
+    printVector(nums);
+
+    return 0;
+}