最简单的题解

#include<bits/stdc++.h>
using namespace std;
stack<char> s;
int main(){
    char c;
    while(cin>>c){
        if(c=='(')s.push('(');
        else if(c==')')s.pop();
    }
    if(s.empty()) cout<<"YES";
    else cout<<"NO";
    return 0;
}