pku2318 自己想的 超时

#include<iostream>
#include<algorithm>
#define MAX 5010
using namespace std;
typedef struct point
{
   double x,y;
};
typedef struct line
{
   point start,end;
};
int max(int x,int y)   
 {   
     return x>y? x:y;   
 }   
 int min(int x,int y)   
 {   
     return x<y? x:y;   
 }   
double multi(point p0,point p1,point p2)//计算矢量[p0,p1],  [p0,p2] 的叉积   
{   
    return (p1.x-p0.x)*(p2.y-p0.y)   
           -(p2.x-p0.x)*(p1.y-p0.y);   
}   
bool is_cross(point s1,point e1,point s2,point e2)//判断直线相交    
{   
   return max(s1.x,e1.x)>=min(s2.x,e2.x)&&   
          max(s2.x,e2.x)>=min(s1.x,e1.x)&&   
          max(s1.y,e1.y)>=min(s2.y,e2.y)&&   
          max(s2.y,e2.y)>=min(s1.y,e1.y)&&   
          multi(s2,e1,s1)*multi(e1,e2,s1)>=0&&   
          multi(s1,e2,s2)*multi(e2,e1,s2)>=0;//加了等号就包括 端点相交    
 }
line b[MAX];
point t;
int ans[MAX];
int main()
{
    int board,toy,i,j,k;
    point Y,X,S;
    while(cin>>board)
    {    if(board==0) break;
          cin>>toy>>Y.x>>Y.y>>X.x>>X.y;
         S.x=Y.x; S.y=X.y;
         memset(ans,0,sizeof(ans));
         for(i=1;i<=board;i++)
           {
             cin>>b[i].start.x>>b[i].end.x;
              b[i].start.y=Y.y;
              b[i].end.y  =X.y;
           }
         for(i=1;i<=toy;i++)
         {
              cin>>t.x>>t.y;k=0;
              for(j=1;j<=board;j++)
              {
                   if(is_cross(S,t,b[j].start,b[j].end))
                       k=j;
              }
              ans[k]=ans[k]+1;
         }
         for(i=0;i<=board;i++)
            cout<<i<<": "<<ans[i]<<endl;
    }
    return 0;
}