NextPermutation2.java

import java.util.Arrays;
import java.util.Scanner;

public class NextPermutation2 {
    public static void main(String[] args) {
        System.out.println("Enter the number of elements in the array");
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n];
        System.out.println("Enter the elements of the array");
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }
        nextPermutation(arr);
        System.out.println(Arrays.toString(arr));

    }

    public static void nextPermutation(int[] nums) {
        int index = -1;
        int n = nums.length;
        for (int i = n - 2; i >= 0; i--) {
            if (nums[i] < nums[i + 1]) {
                index = i;
                break;
            }
            System.out.println(index);
        }
        if (index == -1) {
            reverseArray(nums, 0, n - 1);
            // System.out.println(Arrays.toString(nums));
        } else {
            for (int i = n - 1; i >= index; i--) {
                if (nums[i] > nums[index]) {
                    int temp = nums[i];
                    nums[i] = nums[index];
                    nums[index] = temp;
                    break;
                }

            }
            reverseArray(nums, index + 1, n - 1);
        }

    }

    public static void reverseArray(int[] arr, int start, int end) {
        while (start < end) {
            int temp = arr[start];
            arr[start] = arr[end];
            arr[end] = temp;
            start++;
            end--;
        }
    }

}