二分點所在區域，叉積判斷左右

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
const int N=1005;
int T,n,m,x1,y1,x2,y2,ans[N],cnt[N];
struct dian
{
    double x,y;
    dian(double X=0,double Y=0)
    {
        x=X,y=Y;
    }
    dian operator
 
 + (const dian &a) const
    {
        return dian(x+a.x,y+a.y);
    }
    dian operator - (const dian &a) const
    {
        return dian(x-a.x,y-a.y);
    }
};
struct bian
{
    dian s,t;
    bian(dian S=dian(),dian T=dian())
    {
        s=S,t=T;
    }
}q[N];
bool cmp(const bian &a,const
 
 bian &b)
{
    return a.s.x<b.s.x||(a.s.x==b.s.x&&a.t.x<b.t.x);
}
int read()
{
    int r=0,f=1;
    char p=getchar();
    while(p>‘9‘||p<‘0‘)
    {
        if(p==‘-‘)
            f=-1;
        p=getchar();
    }
    while(p>=‘0‘&&p<=‘9‘)
    {
        r=r*10+p-48;
        p=getchar();
    }
    return
 
 r*f;
}
double cj(dian a,dian b)
{
    return a.x*b.y-a.y*b.x;
}
int main()
{
    while(scanf("%d",&n)&&n)
    {
        memset(ans,0,sizeof(ans));
        memset(cnt,0,sizeof(cnt));
        m=read(),x1=read(),y1=read(),x2=read(),y2=read();
        for(int i=0;i<n;i++)
        {
            int u=read(),l=read();
            q[i]=bian(dian(u,y1),dian(l,y2));
        }
        q[n]=bian(dian(x2,y1),dian(x2,y2));
        sort(q,q+1+n,cmp);
        for(int i=1;i<=m;i++)
        {
            int x=read(),y=read();
            dian p=dian(x,y);
            int l=0,r=n,ans;
            while(l<=r)
            {
                int mid=(l+r)>>1;
                if(cj(q[mid].s-p,q[mid].t-p)<0)
                {
                    ans=mid;
                    r=mid-1;
                }
                else
                l=mid+1;
            }
            cnt[ans]++;
        }
        for(int i=0;i<=n;i++)
            ans[cnt[i]]++;
        puts("Box"); 
        for(int i=1;i<=m;i++)
            if(ans[i])
                printf("%d: %d\n",i,ans[i]);
    }
    return 0;
}

poj 2398 Toy Storage【二分+叉積】