LeetCode_Generate Parentheses

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

For example, given n = 3, a solution set is:

"((()))", "(()())", "(())()", "()(())", "()()()"

　　backtracking solution:

class Solution {
private :
    int n;
    vector<string> result;
public:
   
    vector<string> generateParenthesis(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        rs.clear() ;
        if(n <1 ) return  rs;
        this.n = n;
        string s;
        
        backtracking(s,0,0);
        
        return result ;
        
    }
    void backtracking(string path, int left, int right)
    {
      if(left > n || right > n) return ;
      
      if(path.size() == 2*n )
             result.push_back(path);
             
       if(left+1 <= n)
           backtracking(path+'(', left+1, right );
       if(right+1<= left)
           backtracking(path+')',left, right+1) ;
    
    }



};