1190. Invert the substring between each pair of parentheses

At the beginning of seeing this problem, I felt recursive or Stack do , The recursive version may not be written for a long time , It is not right , Or compromise to the stack .
What is recorded in the stack is the subscript of the left bracket , When you encounter the right parenthesis , Match the left bracket at the top of the stack with it and get out of the stack , Flip all the strings between these two subscripts , barring (), Including nothing . Finally, I'll go through tmp Then take it out () That's it

class Solution {
    
public:
    string reverseParentheses(string s) {
    
        // Recursive flip , Write a function , meet ( To get into , meet ) Quit 
        // Turn the front over , Plus what needs to be flipped later 
        // string res = "";
        // for(int i = 0; i < s.length(); ++i){
    
        // //substr Of c
        // if(s[i] == '('){
    
        // res += reverseParentheses(s.substr(i + 1));
        // }
        // else if(s[i] == ')'){
    
        // reverse(res.begin(),res.end());
        // return res;
        // }
        // else res += s[i];
        // }
        // return res;

        // Bracket matching is still a priority stack better 
        // It is convenient to record subscripts , You can flip from the top of the stack to the current position 
        // What we save in the stack is ( The subscript 
        stack<int> sta;
        string tmp = "";
        for(int i = 0; i < s.length(); ++i){
    
            tmp += s[i];
            if(s[i] == '('){
    
                sta.push(i);
            }
            else if(s[i] == ')'){
    
                int start = sta.top();
                sta.pop();// If the match is lost, it will be out of the stack 
                // The latter parameter is end Can't get , So there's no need to -1
                reverse(tmp.begin() + start + 1, tmp.begin() + i);//+1 Because ( Don't add it 
            }
        }
        string res = "";
        for(char ch : tmp){
    
            if(ch != '(' && ch != ')'){
    
                res += ch;
            }
        }
        return res;
    }
};