@[焜煊辰逸](/space/show?uid=131342)
```
#include<iostream>
using namespace std;
char a[255];
int main(){
int n=0,s=0;
do{
n++;
cin>>a[n];
if(a[n]=='(') s++;
if(a[n]==')') s--;
if(s<0){cout<<"NO";return 0;}//考虑：“)(”,这时s最后为0，但是不合法
}while(a[n]!='@');
if(s==0)cout<<"YES";
else cout<<"NO";
}
```
by 密期望 @ 2019-01-13 21:58:19
@[密期望](/space/show?uid=81705) 谢谢
by 周宇鑫 @ 2019-01-14 09:29:45
优秀
by NOI_LHY @ 2019-01-18 15:52:49