LeetCode Permutations （技巧）

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