题解 | #牛圈围栏问题#

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param n int整型 
     * @return string字符串vector
     */
    vector<string> generateParenthesis(int n) {
        // write code here
        vector<string> res;
        traceback(res, n, 0, 0, "");
        return res;
    }
    void traceback(vector<string> &res,int n,int left, int right, string str){
        if(left + right == 2*n){
            res.push_back(str);
            return;
        }
  
        if(left < n){
            traceback(res, n, left+1, right, str+"(");
        }
        if(left > right){
            traceback(res, n, left, right+1, str+")");
        }
    }

};