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https://github.com/krahets/hello-algo.git
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translation: Add Python and Java code for EN version (#1345)
* Add the intial translation of code of all the languages * test * revert * Remove * Add Python and Java code for EN version
This commit is contained in:
Yudong Jin
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/**
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* File: iteration.java
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* Created Time: 2023-08-24
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* Author: krahets (krahets@163.com)
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*/
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package chapter_computational_complexity;
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public class iteration {
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/* for loop */
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static int forLoop(int n) {
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int res = 0;
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// Loop sum 1, 2, ..., n-1, n
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for (int i = 1; i <= n; i++) {
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res += i;
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}
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return res;
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}
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/* while loop */
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static int whileLoop(int n) {
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int res = 0;
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int i = 1; // Initialize condition variable
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// Loop sum 1, 2, ..., n-1, n
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while (i <= n) {
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res += i;
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i++; // Update condition variable
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}
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return res;
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}
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/* while loop (two updates) */
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static int whileLoopII(int n) {
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int res = 0;
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int i = 1; // Initialize condition variable
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// Loop sum 1, 4, 10, ...
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while (i <= n) {
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res += i;
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// Update condition variable
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i++;
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i *= 2;
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}
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return res;
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}
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/* Double for loop */
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static String nestedForLoop(int n) {
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StringBuilder res = new StringBuilder();
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// Loop i = 1, 2, ..., n-1, n
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for (int i = 1; i <= n; i++) {
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// Loop j = 1, 2, ..., n-1, n
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for (int j = 1; j <= n; j++) {
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res.append("(" + i + ", " + j + "), ");
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}
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}
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return res.toString();
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}
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/* Driver Code */
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public static void main(String[] args) {
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int n = 5;
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int res;
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res = forLoop(n);
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System.out.println("\nSum result of the for loop res = " + res);
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res = whileLoop(n);
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System.out.println("\nSum result of the while loop res = " + res);
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res = whileLoopII(n);
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System.out.println("\nSum result of the while loop (with two updates) res = " + res);
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String resStr = nestedForLoop(n);
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System.out.println("\nResult of the double for loop traversal = " + resStr);
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}
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}
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@@ -0,0 +1,79 @@
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/**
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* File: recursion.java
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* Created Time: 2023-08-24
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* Author: krahets (krahets@163.com)
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*/
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package chapter_computational_complexity;
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import java.util.Stack;
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public class recursion {
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/* Recursion */
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static int recur(int n) {
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// Termination condition
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if (n == 1)
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return 1;
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// Recursive: recursive call
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int res = recur(n - 1);
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// Return: return result
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return n + res;
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}
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/* Simulate recursion with iteration */
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static int forLoopRecur(int n) {
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// Use an explicit stack to simulate the system call stack
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Stack<Integer> stack = new Stack<>();
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int res = 0;
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// Recursive: recursive call
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for (int i = n; i > 0; i--) {
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// Simulate "recursive" by "pushing onto the stack"
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stack.push(i);
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}
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// Return: return result
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while (!stack.isEmpty()) {
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// Simulate "return" by "popping from the stack"
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res += stack.pop();
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}
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// res = 1+2+3+...+n
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return res;
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}
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/* Tail recursion */
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static int tailRecur(int n, int res) {
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// Termination condition
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if (n == 0)
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return res;
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// Tail recursive call
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return tailRecur(n - 1, res + n);
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}
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/* Fibonacci sequence: Recursion */
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static int fib(int n) {
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// Termination condition f(1) = 0, f(2) = 1
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if (n == 1 || n == 2)
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return n - 1;
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// Recursive call f(n) = f(n-1) + f(n-2)
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int res = fib(n - 1) + fib(n - 2);
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// Return result f(n)
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return res;
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}
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/* Driver Code */
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public static void main(String[] args) {
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int n = 5;
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int res;
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res = recur(n);
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System.out.println("\nSum result of the recursive function res = " + res);
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res = forLoopRecur(n);
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System.out.println("\nSum result using iteration to simulate recursion res = " + res);
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res = tailRecur(n, 0);
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System.out.println("\nSum result of the tail-recursive function res = " + res);
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res = fib(n);
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System.out.println("\nThe " + n + "th number in the Fibonacci sequence is " + res);
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}
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}
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/**
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* File: space_complexity.java
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* Created Time: 2022-11-25
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* Author: krahets (krahets@163.com)
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*/
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package chapter_computational_complexity;
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import utils.*;
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import java.util.*;
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public class space_complexity {
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/* Function */
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static int function() {
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// Perform some operations
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return 0;
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}
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/* Constant complexity */
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static void constant(int n) {
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// Constants, variables, objects occupy O(1) space
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final int a = 0;
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int b = 0;
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int[] nums = new int[10000];
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ListNode node = new ListNode(0);
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// Variables in a loop occupy O(1) space
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for (int i = 0; i < n; i++) {
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int c = 0;
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}
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// Functions in a loop occupy O(1) space
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for (int i = 0; i < n; i++) {
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function();
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}
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}
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/* Linear complexity */
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static void linear(int n) {
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// Array of length n occupies O(n) space
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int[] nums = new int[n];
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// A list of length n occupies O(n) space
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List<ListNode> nodes = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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nodes.add(new ListNode(i));
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}
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// A hash table of length n occupies O(n) space
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Map<Integer, String> map = new HashMap<>();
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for (int i = 0; i < n; i++) {
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map.put(i, String.valueOf(i));
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}
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}
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/* Linear complexity (recursive implementation) */
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static void linearRecur(int n) {
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System.out.println("Recursion n = " + n);
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if (n == 1)
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return;
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linearRecur(n - 1);
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}
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/* Quadratic complexity */
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static void quadratic(int n) {
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// Matrix occupies O(n^2) space
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int[][] numMatrix = new int[n][n];
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// A two-dimensional list occupies O(n^2) space
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List<List<Integer>> numList = new ArrayList<>();
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for (int i = 0; i < n; i++) {
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List<Integer> tmp = new ArrayList<>();
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for (int j = 0; j < n; j++) {
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tmp.add(0);
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}
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numList.add(tmp);
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}
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}
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/* Quadratic complexity (recursive implementation) */
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static int quadraticRecur(int n) {
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if (n <= 0)
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return 0;
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// Array nums length = n, n-1, ..., 2, 1
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int[] nums = new int[n];
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System.out.println("Recursion n = " + n + " in the length of nums = " + nums.length);
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return quadraticRecur(n - 1);
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}
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/* Exponential complexity (building a full binary tree) */
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static TreeNode buildTree(int n) {
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if (n == 0)
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return null;
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TreeNode root = new TreeNode(0);
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root.left = buildTree(n - 1);
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root.right = buildTree(n - 1);
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return root;
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}
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/* Driver Code */
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public static void main(String[] args) {
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int n = 5;
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// Constant complexity
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constant(n);
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// Linear complexity
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linear(n);
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linearRecur(n);
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// Quadratic complexity
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quadratic(n);
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quadraticRecur(n);
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// Exponential complexity
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TreeNode root = buildTree(n);
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PrintUtil.printTree(root);
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}
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}
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@@ -0,0 +1,167 @@
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/**
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* File: time_complexity.java
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* Created Time: 2022-11-25
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* Author: krahets (krahets@163.com)
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*/
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package chapter_computational_complexity;
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public class time_complexity {
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/* Constant complexity */
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static int constant(int n) {
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int count = 0;
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int size = 100000;
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for (int i = 0; i < size; i++)
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count++;
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return count;
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}
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/* Linear complexity */
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static int linear(int n) {
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int count = 0;
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for (int i = 0; i < n; i++)
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count++;
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return count;
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}
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/* Linear complexity (traversing an array) */
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static int arrayTraversal(int[] nums) {
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int count = 0;
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// Loop count is proportional to the length of the array
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for (int num : nums) {
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count++;
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}
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return count;
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}
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/* Quadratic complexity */
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static int quadratic(int n) {
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int count = 0;
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// Loop count is squared in relation to the data size n
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < n; j++) {
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count++;
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}
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}
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return count;
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}
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/* Quadratic complexity (bubble sort) */
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static int bubbleSort(int[] nums) {
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int count = 0; // Counter
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// Outer loop: unsorted range is [0, i]
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for (int i = nums.length - 1; i > 0; i--) {
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// Inner loop: swap the largest element in the unsorted range [0, i] to the right end of the range
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for (int j = 0; j < i; j++) {
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if (nums[j] > nums[j + 1]) {
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// Swap nums[j] and nums[j + 1]
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int tmp = nums[j];
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nums[j] = nums[j + 1];
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nums[j + 1] = tmp;
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count += 3; // Element swap includes 3 individual operations
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}
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}
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}
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return count;
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}
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/* Exponential complexity (loop implementation) */
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static int exponential(int n) {
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int count = 0, base = 1;
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// Cells split into two every round, forming the sequence 1, 2, 4, 8, ..., 2^(n-1)
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < base; j++) {
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count++;
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}
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base *= 2;
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}
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// count = 1 + 2 + 4 + 8 + .. + 2^(n-1) = 2^n - 1
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return count;
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}
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/* Exponential complexity (recursive implementation) */
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static int expRecur(int n) {
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if (n == 1)
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return 1;
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return expRecur(n - 1) + expRecur(n - 1) + 1;
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}
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/* Logarithmic complexity (loop implementation) */
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static int logarithmic(int n) {
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int count = 0;
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while (n > 1) {
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n = n / 2;
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count++;
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}
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return count;
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}
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/* Logarithmic complexity (recursive implementation) */
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static int logRecur(int n) {
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if (n <= 1)
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return 0;
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return logRecur(n / 2) + 1;
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}
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/* Linear logarithmic complexity */
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static int linearLogRecur(int n) {
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if (n <= 1)
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return 1;
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int count = linearLogRecur(n / 2) + linearLogRecur(n / 2);
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for (int i = 0; i < n; i++) {
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count++;
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}
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return count;
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}
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/* Factorial complexity (recursive implementation) */
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static int factorialRecur(int n) {
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if (n == 0)
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return 1;
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int count = 0;
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// From 1 split into n
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for (int i = 0; i < n; i++) {
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count += factorialRecur(n - 1);
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}
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return count;
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}
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/* Driver Code */
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public static void main(String[] args) {
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// Can modify n to experience the trend of operation count changes under various complexities
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int n = 8;
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System.out.println("Input data size n = " + n);
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int count = constant(n);
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System.out.println("Number of constant complexity operations = " + count);
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count = linear(n);
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System.out.println("Number of linear complexity operations = " + count);
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count = arrayTraversal(new int[n]);
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System.out.println("Number of linear complexity operations (traversing the array) = " + count);
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count = quadratic(n);
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System.out.println("Number of quadratic order operations = " + count);
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int[] nums = new int[n];
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for (int i = 0; i < n; i++)
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nums[i] = n - i; // [n,n-1,...,2,1]
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count = bubbleSort(nums);
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System.out.println("Number of quadratic order operations (bubble sort) = " + count);
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count = exponential(n);
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System.out.println("Number of exponential complexity operations (implemented by loop) = " + count);
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count = expRecur(n);
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System.out.println("Number of exponential complexity operations (implemented by recursion) = " + count);
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count = logarithmic(n);
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System.out.println("Number of logarithmic complexity operations (implemented by loop) = " + count);
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count = logRecur(n);
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System.out.println("Number of logarithmic complexity operations (implemented by recursion) = " + count);
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count = linearLogRecur(n);
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System.out.println("Number of linear logarithmic complexity operations (implemented by recursion) = " + count);
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count = factorialRecur(n);
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System.out.println("Number of factorial complexity operations (implemented by recursion) = " + count);
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}
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}
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@@ -0,0 +1,50 @@
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/**
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* File: worst_best_time_complexity.java
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* Created Time: 2022-11-25
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* Author: krahets (krahets@163.com)
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*/
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package chapter_computational_complexity;
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import java.util.*;
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public class worst_best_time_complexity {
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/* Generate an array with elements {1, 2, ..., n} in a randomly shuffled order */
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static int[] randomNumbers(int n) {
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Integer[] nums = new Integer[n];
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// Generate array nums = { 1, 2, 3, ..., n }
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for (int i = 0; i < n; i++) {
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nums[i] = i + 1;
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}
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// Randomly shuffle array elements
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Collections.shuffle(Arrays.asList(nums));
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// Integer[] -> int[]
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int[] res = new int[n];
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for (int i = 0; i < n; i++) {
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res[i] = nums[i];
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}
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return res;
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}
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/* Find the index of number 1 in array nums */
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static int findOne(int[] nums) {
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for (int i = 0; i < nums.length; i++) {
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// When element 1 is at the start of the array, achieve best time complexity O(1)
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// When element 1 is at the end of the array, achieve worst time complexity O(n)
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if (nums[i] == 1)
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return i;
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}
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return -1;
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}
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/* Driver Code */
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public static void main(String[] args) {
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for (int i = 0; i < 10; i++) {
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int n = 100;
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int[] nums = randomNumbers(n);
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int index = findOne(nums);
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System.out.println("\nThe array [ 1, 2, ..., n ] after being shuffled = " + Arrays.toString(nums));
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System.out.println("The index of number 1 is " + index);
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}
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}
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}
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