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;
}
}
}