更简单

#include <bits/stdc++.h>
using namespace std;
stack<char>s;
int main(){
    string s1;
    cin >> s1;
    for(int i = 0;i<s1.size();i++){
        char ch=s1[i];
        if(ch=='('||ch=='['||ch=='{'){
            s.push(ch);
        }else{
            if(!s.empty()&&(s.top()=='('&&ch==')'||s.top()=='['&&ch==']'||s.top()=='{'&&ch=='}')){
                s.pop();
            }
        }
    }
    if(s.empty()){
        cout << "true";
    }else{
        cout << "false";
    }
    return 0;
}