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> ans;
    void dfs(string path, int left, int right) {
        if (left < 0 || right < 0) return;
        if (left == 0 && right == 0) {
            ans.push_back(path);
            return;
        }
        if (left > right) return;
        dfs(path+"(", left-1, right);
        dfs(path+")", left, right-1);
    }
    vector<string> generateParenthesis(int n) {
        // write code here
        dfs("", n, n);
        return ans;
    }
};