LeetCode: Generate Parentheses

Title:

https://leetcode.com/problems/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:

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

思路：DFS搜索。每次首先是（，然后是）。用两个值表示（括号当前可以用的数目n和）括号当前可用的数目m。）可以使用的前提是m>n

vector<string> generateParenthesis(int n){
        vector<string> result;
        if (n == 0)
            return result;
        string s;
        generate(result,s,n,n);
        return result;
    }
    void generate(vector<string> & result,string s, int n,int m){
        if (n == 0 && m == 0){
            result.push_back(s);
        }
        if (n > 0){
            generate(result,s+'(',n-1,m);
        }
        if (n < m && m > 0){
                generate(result,s+')',n,m-1);
        }

    }