牛客 括号画家题解（栈模板题）

    #include<iostream>
    #include<bits/stdc++.h>
    
    using namespace std;
    
    int rv;
    
    int main()
    {
    	string s;
    	int r1 = 0, r2 = 0;
    	cin>>s;
    	stack<char>st;
    	for(int i = 0; i < s.size(); i ++ ){
    		if(s[i] == '(' || s[i] == '[' || s[i] == '{'){
    			st.push(s[i]);
    		}
    		else{
    			if(!st.empty()){
    				if((s[i] == ')' && st.top() == '(') || (s[i] == ']' && st.top() == '[') || (s[i] == '}' && st.top() == '{')){
    					st.pop();
    					r1 += 2;
    				}
    				else{
    					r2 = max(r1, r2);
    					r1 = 0;
    					while(