LeetCode OJ：Generate Parentheses（括号生成）

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:

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

 求出所有可能的括号组合，在dfs加上回溯条件，右括号数目不能超过左括号，还有就是左括号数最大不能超过n，代码如下：

class Solution {
public:
    vector<string> generateParenthesis(int n) {
        dfs(0,n*2,0,0,"");
        return ret;
    }

    void dfs(int dep, int maxDep, int left, int leftTotal, string curr){
        if(leftTotal*2 > maxDep)
            return;
        if(dep == maxDep){
            ret.push_back(curr);
            return;
        }
        for(int i = 0; i < 2; i++){
            if(i == 0){
                dfs(dep+1, maxDep, left+1, leftTotal+1, curr+"(");
            }else{
                if(left)
                    dfs(dep+1, maxDep, left-1, leftTotal, curr+")");
            }
        }
    }
private:
    vector<string> ret;
};