poj2318 TOYS

http://poj.org/problem?id=2318

//叉积应用

#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;

#define N 5010

struct P
{
    int x1;
    int x2;
}pt[N];

int n,m,x1,y1,x2,y2;

int toy[N];

bool left(int x,int y,struct P a)
{
    if(x<a.x2+(y-y2)*(a.x1-a.x2)*1.0/(y1-y2))
        return true;
    return false;
}

int binary_search(int x,int y)        //二分查找
{
    int l=0,r=n;
    int mid;
    while(l<r)
    {
        mid=(l+r)/2;
        if(left(x,y,pt[mid]))
            r=mid;
        else
            l=mid+1;
    }
    return l;
}

int main()
{
    int i,x,y;
    while(scanf("%d",&n)!=EOF&&n)
    {
        scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2);
        memset(toy,0,sizeof(toy));
        for(i=0;i<n;i++)
        {
            scanf("%d%d",&pt[i].x1,&pt[i].x2);
        }
        for(i=0;i<m;i++)
        {
            scanf("%d%d",&x,&y);
            toy[binary_search(x,y)]++;
        }
        for(i=0;i<=n;i++)
            printf("%d: %d\n",i,toy[i]);
        printf("\n");
    }
    return 0;
}