Next_Permutation.java

import java.util.Arrays;
 
public class nextPermutation {
    public static int[] swap(int data[], int left, int right)
    {
        int temp = data[left];
        data[left] = data[right];
        data[right] = temp;
        return data;
    }
    public static int[] reverse(int data[], int left, int right)
    {
        while (left < right) {
            int temp = data[left];
            data[left++] = data[right];
            data[right--] = temp;
        }

        return data;
    }
    public static boolean findNextPermutation(int data[])
    {
        if (data.length <= 1)
            return false;
 
        int last = data.length - 2;

        while (last >= 0) {
            if (data[last] < data[last + 1]) {
                break;
            }
            last--;
        }

        if (last < 0)
            return false;
 
        int nextGreater = data.length - 1;

        for (int i = data.length - 1; i > last; i--) {
            if (data[i] > data[last]) {
                nextGreater = i;
                break;
            }
        }
        data = swap(data, nextGreater, last);
 
        data = reverse(data, last + 1, data.length - 1);
 
        return true;
    }
    public static void main(String args[])
    {
        int data[] = { 1, 2, 3 };
        if (!findNextPermutation(data))
            System.out.println("There is no higher"
                               + " order permutation "
                               + "for the given data.");
        else {
            System.out.println(Arrays.toString(data));
        }
    }
}