[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:

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

递归与深搜。

class Solution {
public:
    void getRes(vector<string> &res, int st, string str, int count, int n) {
        if (str.length() > 2 * n || st > n) return;
        if (count == n && st == 0) {
            res.push_back(str);
            return;
        }
        getRes(res, st + 1, str + '(', count, n);
        if (st > 0) getRes(res, st - 1, str + ')', count + 1, n);
    }
    
    vector<string> generateParenthesis(int n) {
        vector<string> res;
        getRes(res, 0, "", 0, n);
        return res;
    }
};