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

Generate Parentheses.cpp

class Solution {
public:
    vector<string> generateParenthesis(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<string> result;
        
        calc(result, "", n, 0);
        
        return result;
    }
    
    void calc(vector<string>& result, string cur,int left, int right) {
        if(left == 0 and right == 0) {
            result.push_back(cur);
            return;
        }
        
        if(left > 0) {
            calc(result, cur + '(', left - 1, right + 1);
        }
        
        if(right > 0) {
            calc(result, cur + ')', left, right - 1);
        }
    }
};