NYOJ---括号匹配问题---栈的使用

http://acm.nyist.net/JudgeOnline/problem.php?pid=2

这题比较水，不注释了：

#include<iostream>
#include<cstring>
#include<cmath>
#include<vector>
#include <list>
#include <stack>
using namespace std;
bool ismatch(char &a,char &b)
{
	if(a=='('&&b==')'||a=='['&&b==']')return 1;
	return 0;
}
int main()
{
	int N;
	cin>>N;
	stack<char> a;
	while(N--)
	{
		while(!a.empty())a.pop();
		string s;
		cin>>s;
		for(int i=0;i!=s.size();i++)
		{
			char tmp=s[i];
			if( a.empty() || !ismatch(a.top(),tmp))a.push(tmp);
			else a.pop();
		}
		if(a.empty())cout<<"Yes"<<endl;
		else cout<<"No"<<endl;
	}
	return 0;
}