面试题 08.07. 无重复字符串的排列组合

 1 class Solution {
 2     vector<string>ans;
 3     void backtracking(string &s,int start)
 4     {
 5         if(start==s.size())
 6         {
 7             ans.emplace_back(s);
 8         }
 9         for(size_t i=start;i<s.size();++i)
10         {
11             swap(s[i],s[start]);
12             backtracking(s,start+1);
13             swap(s[i],s[start]);
14         }
15     }
16 public:
17     vector<string> permutation(string S) 
18     {
19         backtracking(S,0);
20         return ans;
21     }
22 };