next_permutation in Java

Sequence

1. Find the longest non-increasing suffix and find the pivot.
2. If the suffix is the whole array, then there is no higher order permutation for the data.
3. Find the rightmost successor to the pivot.
4. Swap the successor and the pivot.
5. Reverse the suffix.

// Java program to implement
// the next_permutation method

import java.util.Arrays;

public class nextPermutation {

    // Function to swap the data
    // present in the left and right indices
    public static int[] swap(int data[], int left, int right)
    {

        // Swap the data
        int temp = data[left];
        data[left] = data[right];
        data[right] = temp;

        // Return the updated array
        return data;
    }

    // Function to reverse the sub-array
    // starting from left to the right
    // both inclusive
    public static int[] reverse(int data[], int left, int right)
    {

        // Reverse the sub-array
        while (left < right) {
            int temp = data[left];
            data[left++] = data[right];
            data[right--] = temp;
        }

        // Return the updated array
        return data;
    }

    // Function to find the next permutation
    // of the given integer array
    public static boolean findNextPermutation(int data[])
    {

        // If the given dataset is empty
        // or contains only one element
        // next_permutation is not possible
        if (data.length <= 1)
            return false;

        int last = data.length - 2;

        // find the longest non-increasing suffix
        // and find the pivot
        while (last >= 0) {
            if (data[last] < data[last + 1]) {
                break;
            }
            last--;
        }

        // If there is no increasing pair
        // there is no higher order permutation
        if (last < 0)
            return false;

        int nextGreater = data.length - 1;

        // Find the rightmost successor to the pivot
        for (int i = data.length - 1; i > last; i--) {
            if (data[i] > data[last]) {
                nextGreater = i;
                break;
            }
        }

        // Swap the successor and the pivot
        data = swap(data, nextGreater, last);

        // Reverse the suffix
        data = reverse(data, last + 1, data.length - 1);

        // Return true as the next_permutation is done
        return true;
    }

    // Driver Code
    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));
        }
    }
}