poj 2398 Toy Storage【二分+叉积】

二分点所在区域，叉积判断左右

#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;
}