Leetcode-Generate Parentheses(递归）

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:

[  "((()))",  "(()())",  "(())()",  "()(())",  "()()()"]

class Solution {public:    vector<string> generateParenthesis(int n) {        vector<string> res;        addinger(res,"",n,0);        return res;    }    void addinger(vector<string> &v,string str,int n,int m){        if(n==0&&m==0){            v.push_back(str);            return;        }        if(m>0)        addinger(v,str+")",n,m-1);        if(n>0)        addinger(v,str+"(",n-1,m+1);    }    };