【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:

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

 

class Solution {
public:
    void unguarded_generate(vector<string> &result,string curr,int m,int n)
    {
        if (m==0&&n==0)
        {
            result.push_back(curr);
        }
        else
        {
            if(m!=0)
            {
                unguarded_generate(result,curr+"(",m-1,n);
            }
        
            if(m<n&&n!=0)
            {
                unguarded_generate(result,curr+")",m,n-1);
            }
        }
    }
 
    vector<string> generateParenthesis(int n) 
    {
        vector<string> ret;
        if(n>0)
        {
            unguarded_generate(ret,string(),n,n);
        }
        return ret;
    }
};