Problem46.java

import java.util.*;

class Problem46 {
	public static void main(String[] args) {
		int[] nums = new int[]{1, 2, 3, 4};
		System.out.println(new Problem46().permute(nums));
	}

	public List<List<Integer>> permute(int[] nums) {
 List<List<Integer>> list = new ArrayList<>();
 permute(list, nums, 0);
 return list;
 }

 public void permute(List<List<Integer>> list, int[] nums, int start) {
 	List<Integer> res = new ArrayList<>();
 	if(start == nums.length-1) {
 		return;
 	} else {
 		permute(list, nums, start++);
 		if (list.size() > 0) {
 			for (int i =0; i < list.size(); i++) {
 				list.get(i).add(nums[start]);
 			}
 		}
 	}
 }
}