POJ-2398 Toy Storage

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
using namespace std;
const int maxn = 5000+50;
int ans[maxn];
struct Point
{
    int x,y;
    Point(){}
    Point(int _x,int _y)
    {
        x = _x;y = _y;
    }
    Point operator -(const Point &b)const
    {
        return Point(x - b.x,y - b.y);
    }
    int operator *(const Point &b)const
    {
        return x*b.x + y*b.y;
    }
    int operator ^(const Point &b)const
    {
        return x*b.y - y*b.x;
    }
};
struct Line
{
    Point s,e;
    Line(){}
    Line(Point _s,Point _e)
    {
        s = _s;e = _e;
    }
    bool operator < (const Line &rhs) const{
       if(s.x==rhs.s.x) return e.x<rhs.e.x;
       return s.x<rhs.s.x;
    }
};

int xmult(Point p0,Point p1,Point p2)
{
    return (p1-p0)^(p2-p0);
}
Line line[maxn];
int num[maxn];
int main()
{
    int n,m,x1,x2,y1,y2;
    while(scanf("%d",&n)==1&&n){
        scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2);
        int Ui,Li;
        for(int i=0;i<n;i++){
            scanf("%d%d",&Ui,&Li);
            line[i]=Line(Point(Ui,y1),Point(Li,y2));
        }
        line[n]=Line(Point(x2,y1),Point(x2,y2));
        sort(line,line+n+1);
        int x,y;
        Point p;
        memset(ans,0,sizeof(ans));
        while(m--){
            scanf("%d %d",&x,&y);
            p=Point(x,y);
            int l=0,r=n;
            int tmp;
            while(l<=r){
                int mid=(l+r)/2;
                if(xmult(p,line[mid].s,line[mid].e)<0){
                    tmp=mid;
                    r=mid-1;
                }
                else l=mid+1;
            }
            ans[tmp]++;
        }
        printf("Box\n");
        memset(num,0,sizeof(num));
        for(int i=0;i<=n;i++)
            if(ans[i]>0) num[ans[i]]++;
        for(int i=0;i<=n;i++)
            if(num[i]>0) printf("%d: %d\n",i,num[i]);
    }
    return 0;
}