leetcode--Permutations

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1],[3,1,2], and [3,2,1].

public class Solution {    public List<List<Integer>> permute(int[] nums) {List<List<Integer>> res = new ArrayList<List<Integer>>();solve(nums, 0, res);return res;    }    public void solve(int[] nums,int i,List<List<Integer>> res){if(i==nums.length-1){List<Integer> t = new ArrayList<Integer>();for(int j=0;j<nums.length;j++){t.add(nums[j]);}res.add(t);}for(int j=i;j<nums.length;j++){int t = nums[i];nums[i] = nums[j];nums[j] = t;solve(nums, i+1, res);t = nums[i];nums[i] = nums[j];nums[j] = t;}}}