UVa 10167 Birthday Cake

UVa 10167 Birthday Cake

采用枚举。
首先，Ax+By=0必须表示直线，即A、B不能同时为0；另外，要注意到直线不能过输入中的2N个点；检测点在直线的哪一侧，只需要简单的线性规划的知识。
以下是我的代码：

#include < cstdio >
using   namespace  std;
const   int  kMaxn( 57 );

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

     int  n;
     while (scanf( " %d " , & n) == 1   &&  n)
    {
         int  x[kMaxn << 1 ],y[kMaxn << 1 ];
         for ( int  i = 1 ;i <= (n << 1 );i ++ )
            scanf( " %d%d " , & x[i], & y[i]);

         bool  found( false );
         int  a,b;
         for ( int  i =- 500 ;i <= 500   &&   ! found;i ++ )
             for ( int  j =- 500 ;j <= 500   &&   ! found;j ++ )
            {
                 if (i == 0   &&  j == 0 )
                     continue ;
                 bool  cannot( false );
                 for ( int  k = 1 ;k <= (n << 1 );k ++ )
                     if (i * x[k] + j * y[k] == 0 )
                    {
                        cannot = true ;
                         break ;
                    }
                 if (cannot)
                     continue ;
                 int  t( 0 );
                 for ( int  k = 1 ;k <= (n << 1 );k ++ )
                     if (i * x[k] + j * y[k] < 0 )
                        t ++ ;
                 if (t == n)
                {
                    a = i;
                    b = j;
                    found = true ;
                }
            }

        printf( " %d %d\n " ,a,b);
    }

     return   0 ;
}