LeetCode - Permutations

 1 class Solution {
 2 public:
 3     vector<vector<int> > permute(vector<int> &num) {
 4         int n = num.size();
 5         vector<vector<int> > ret;
 6         if (n == 0)
 7             return ret;
 8         if (n == 1)
 9         {
10             ret.push_back(num);
11             return ret;
12         }
13         vector<int> cur;
14         vector<int> tmp;
15         vector<vector<int> > post;
16         
17         //每次取1个数字
18         for (int i = 0; i < n; i++)
19         {
20             cur = num;
21             //剩下的数作全排列
22             cur.erase(cur.begin()+i);
23             post = permute(cur);
24             //将取出的数字放第一位
25             for (int j = 0; j < post.size(); j++)
26             {
27                 tmp = post[j];
28                 tmp.insert(tmp.begin(), num[i]);
29                 ret.push_back(tmp);
30             }
31         }
32         return ret;
33     }
34 };