题解 | #括号生成#

class Solution {
public:
    void recursion(int left, int right, string temp, vector<string> &res, int n){
        //左右括号都用完了，就加入结果
        if(left == n && right == n){ 
            res.push_back(temp);
            return;
        }
        //使用一次左括号
        if(left < n) 
            recursion(left + 1, right, temp + "(", res, n);
        //使用右括号个数必须少于左括号
        if(right < n && left > right) 
            recursion(left, right + 1, temp + ")", res, n);
    }
    
    vector<string> generateParenthesis(int n) {
        //记录结果
        vector<string> res; 
        //记录每次组装的字符串
        string temp; 
        //递归
        recursion(0, 0, temp, res, n); 
        return res;
    }
};