**本蒟蒻来也**
by leiwenjin1234 @ 2023-10-12 20:58:05
**访问栈顶先判空**
```cpp
#include<bits/stdc++.h>
using namespace std;
stack <char> s;
char a[300];
int len;
int main(){
cin>>a;
len=strlen(a);
for(int i=0;i<len;i++){
if(a[i]=='(') s.push(a[i]);
if(a[i]==')'){
if(!s.empty()&&s.top()=='(') s.pop();
}
}
if(s.empty()) printf("YES");
else printf("NO");
return 0;
}
```
90 分 1WA
by leiwenjin1234 @ 2023-10-12 21:01:11
@[leiwenjin1234](/user/921176) 感谢大佬，自己按照思路AC了
```cpp
#include<bits/stdc++.h>
using namespace std;
stack <char> s;
char a[300];
int len;
int main(){
cin>>a;
len=strlen(a);
for(int i=0;i<len;i++){
if(s.empty() && a[i]==')'){
printf("NO");
return 0;
}
if(a[i]=='(') s.push(a[i]);
if(a[i]==')'){
if(s.top()=='(') s.pop();
}
}
if(s.empty()) printf("YES");
else printf("NO");
return 0;
}
```
by Ying_Sophia @ 2023-10-12 21:03:14
手真快，我还在改呢
by leiwenjin1234 @ 2023-10-12 21:04:02
@[leiwenjin1234](/user/921176) ο(=•ω＜=)ρ⌒☆
by Ying_Sophia @ 2023-10-12 21:04:55
等等，你都没把）入栈，为什么要判断栈顶啊？
by Y_QWQ_Y @ 2023-12-15 19:45:48