UVA 673（括号配对）

#include<iostream>
#include<stack>
using namespace std;
const int maxn=130;
int main()
{
int n;
cin>>n;
cin.get();
while(n--)
{
int k=1;
stack<char>a;
char ch;
while(cin.get(ch)&&ch!='\n')
{
if(ch==')'&&k)
{
if(a.empty())
k=0;
else if(a.top()='(')
a.pop();
else
k=0;

}
else if(ch==']'&&k)
{
if(a.empty())
k=0;
else  if(a.top()=='[')
a.pop();
else
k=0;

}
else
a.push(ch);

}
if(a.empty()&&k)
cout<<"Yes"<<endl;
else
cout<<"No"<<endl;

}
return 0;
}