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package backtracking;

import java.util.ArrayList;

import java.util.List;

/**

* Created by gouthamvidyapradhan on 15/03/2017. Given a collection of distinct numbers, return all

* possible permutations.

*

* <p>For example, [1,2,3] have the following permutations: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1],

* [3,1,2], [3,2,1] ]

*/

public class Permutations {

/**

* Main method

*

* @param args

* @throws Exception

*/

public static void main(String[] args) throws Exception {

int[] nums = {1, 2, 3};

List<List<Integer>> result = new Permutations().permute(nums);

}

public List<List<Integer>> permute(int[] nums) {

List<List<Integer>> result = new ArrayList<>();

nextPermutation(0, nums, result);

return result;

}

private void nextPermutation(int i, int[] nums, List<List<Integer>> result) {

if (i == nums.length - 1) {

List<Integer> list = new ArrayList<>();

for (int n : nums) list.add(n);

result.add(list);

} else {

for (int j = i, l = nums.length; j < l; j++) {

int temp = nums[j];

nums[j] = nums[i];

nums[i] = temp;

nextPermutation(i + 1, nums, result);

temp = nums[j];

nums[j] = nums[i];

nums[i] = temp;

}

}

}

}