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:

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

题意：给你左右括号的个数，问你可以组成完全匹配的个数。

思路：递归：也就两种选择，要么左括号，要么右括号，分别记录个数；只要左括号的个数大于0的话，那么就可以填写左括号；右括号的话，那么要确保此时的序列，左括号的个数要大于右括号的个数。

class Solution {public:    void print(int left, int right, string s, vector<string> &result) {        if (left == 0 && right == 0) {            result.push_back(s);        }        if (left > 0) {            print(left-1, right, s+'(', result);        }        if (right > 0 && left < right) {            print(left, right-1, s+')', result);        }     }    vector<string> generateParenthesis(int n) {        vector<string> result;        string tmp = "";        print(n, n, tmp, result);        return result;    }};