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].

思路：这题和string permutation差不多，依旧是枚举互换的位置。

 1 class Solution {
 2 public:
 3     void permuteRecur(vector<vector<int> >& res, int st_loc, vector<int>& aim)
 4     {
 5         if (st_loc >= aim.size())
 6             res.push_back(aim);
 7         else
 8         {
 9             for (int i = st_loc, n = aim.size(); i < n; i++)
10             {
11                 swap(aim[st_loc], aim[i]);
12                 permuteRecur(res, st_loc + 1, aim);
13                 swap(aim[st_loc], aim[i]);
14             }
15         }
16     }
17     vector<vector<int>> permute(vector<int>& nums) {
18         vector<vector<int> > res;
19         permuteRecur(res, 0, nums);
20         return res;
21     }
22 };