Problem no. 287.java

// Ques : Find the duplicate number 
// Ques Link : https://leetcode.com/problems/find-the-duplicate-number/ 



package com.nitin;

import java.util.Arrays;

public class findDuplicate {
    public static void main(String[] args) {
        int[] arr = {1,3,4,2,5,5};
        System.out.println(duplicate(arr));
    }

    public static int duplicate(int[] arr) {
        int i = 0;
        while (i < arr.length) {
            if (arr[i] != i + 1) {
                int correct = arr[i] - 1;
                if (arr[i] != arr[correct]) {
                    swap(arr, i, correct);
                } else {
                    return arr[i];
                }
            } else {
                i++;
            }
        }
        return -1;
    }

    static void swap(int[] arr, int first, int second) {
        int temp = arr[first];
        arr[first] = arr[second];
        arr[second] = temp;
    }
}