面试题 08.09：括号

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

class Solution {
public:
    vector<char> sign={'(',')'};
    string path;
    vector<string> res;
    void backtracing(int n,int left,int right){
        if(left>n||right>n||left<right) return;
        if(left==n&&right==n){
            res.push_back(path);
            return;
        }
        for(char c:sign){
            path.push_back(c);
            if(c=='(') backtracing(n,left+1,right);//优先左括号
            else backtracing(n,left,right+1);
            path.pop_back();
        }
    }
    vector<string> generateParenthesis(int n) {
        backtracing(n,0,0);
        return res;
    }
};