package Leetcode;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.stream.Collectors;

public class Permutations

{

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

{

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

if( nums == null || nums.length == 0 )

return result;

permuteRecursive( nums, result, 0, new ArrayList<Integer>() );

return result;

}

private void permuteRecursive( int[] nums, List<List<Integer>> result, int currentIndex,

List<Integer> currentResult )

{

if( currentIndex == nums.length )

{

result.add( currentResult );

return;

}

for( int i = currentIndex; i < nums.length; i++ )

{

swap(nums, i, currentIndex);

List<Integer> list = Arrays.stream(nums).boxed().collect(Collectors.toList());

permuteRecursive( nums, result, currentIndex + 1, list );

swap(nums, currentIndex, i);

}

}

private void swap(int[] nums, int i, int j)

{

int temp = nums[i];

nums[i] = nums[j];

nums[j] = temp;

}

public static void main( String[] args )

{

TreeNode root = new TreeNode( 2 );

root.left = new TreeNode( 1 );

root.right = new TreeNode( 3 );

Permutations obj = new Permutations();

List<List<Integer>> numsList = obj.permute( new int[] {1,2,3} );

System.out.println( numsList );

}

}