https://leetcode.com/problems/generate-parentheses/

generate-parentheses.cpp

class Solution 
{
public:
    vector<string> generateParenthesis(int n)
    {
        vector<string> rst;
        string str;
        gpdfs(n, n, str, rst);
        return rst;
    }

    void gpdfs(int left, int right, string str, vector<string>& rst)
    {
        if (left == 0 && right == 0)
        {
            rst.push_back(str);
            return;
        }
        else if (left > right)
            return;
        else
        {
            if (left > 0) gpdfs(left - 1, right, str + "(", rst);
            if (right > 0) gpdfs(left, right - 1, str + ")", rst);
        }
        return;
    }
};

12 ms | 14 MB

Runtime: 4 ms, faster than 99.68% of C++ online submissions for Generate Parentheses.
Memory Usage: 17.4 MB, less than 34.10% of C++ online submissions for Generate Parentheses.