UVa 673 Parentheses Balance

UVa 673 Parentheses Balance

和上午做的某一题类似，比那一题还简单点。不过我却犯了同样的错误！
最终成功的条件不仅是没有遇到匹配失误，栈还必须为空！
以下是我的代码：

#include < iostream >
#include < stack >
#include < string >
#include < cstdio >
using   namespace  std;

int  main()
{
     /*
    freopen("data.in","r",stdin);
    freopen("data.out","w",stdout);
    // */

     int  n;
    cin >> n;
    cin. get ();
     for ( int  i = 1 ;i <= n;i ++ )
    {
         string  t;
        getline(cin,t);

        stack < char >  s;
         bool  fail( false );
         for ( int  j = 0 ;j < t.size();j ++ )
             if (t[j] == ' ( '   ||  t[j] == ' [ ' )
                s.push(t[j]);
             else   if (t[j] == ' ) ' )
            {
                 if (s.empty()  ||  s.top() != ' ( ' )
                {
                    fail = true ;
                     break ;
                }
                 else
                    s.pop();
            }
             else   if (t[j] == ' ] ' )
            {
                 if (s.empty()  ||  s.top() != ' [ ' )
                {
                    fail = true ;
                     break ;
                }
                 else
                    s.pop();
            }

         if ( ! fail  &&  s.empty())
            cout << " Yes " << endl;
         else
            cout << " No " << endl;
    }

     return   0 ;
}