【leetcode】Generate Parentheses

 1 class Solution {
 2 
 3 public:
 4 
 5     vector<string> generateParenthesis(int n) {
 6 
 7        
 8 
 9         vector<string> result;
10 
11         generate(result,"",0,n,0,0);
12 
13         return result;
14 
15        
16 
17     }
18 
19    
20 
21     void generate(vector<string> &result,string tmp,int index,int &n,int leftNum,int rightNum)
22 
23     {
24 
25         if(leftNum>n||rightNum>n||rightNum>leftNum)
26 
27         {
28 
29             return;
30 
31         }
32 
33         if(index==2*n)
34 
35         {
36 
37             result.push_back(tmp);
38 
39             return;
40 
41         }
42 
43        
44 
45         generate(result,tmp+"(",index+1,n,leftNum+1,rightNum);
46 
47         generate(result,tmp+")",index+1,n,leftNum,rightNum+1);
48 
49     }
50 
51 };