POJ2398+几何+排序

题意：

给定一些线段的两端和一些点。

问某些区域出现的点的个数的次数。。。

题目给定的线段未排序！！！

/*
几何+排序
*/
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<algorithm>
#include<iostream>
using namespace std;
const int maxn = 1005;
const double eps = 1e-8;
struct point {
    double x,y;
};
struct Line {
    point u,d;
}line[ maxn ];
int cnt[ maxn ],vis[ maxn ];
double xmult( point sp,point ep,point op ){
    return ( sp.x-op.x )*( ep.y-op.y )-( sp.y-op.y )*( ep.x-op.x );
}
int cmp( Line a,Line b ){
    return ( a.u.x+a.d.x )<( b.u.x+b.d.x );
}
int main(){
    int n,m;
    double x1,x2,y1,y2;
    while( scanf("%d",&n),n ){
        scanf("%d%lf%lf%lf%lf",&m,&x1,&y1,&x2,&y2);
        line[ 0 ].u.x = x1,line[ 0 ].u.y = y1;
        line[ 0 ].d.x = x1,line[ 0 ].d.y = y2;
        for( int i=1;i<=n;i++ ){
            scanf("%lf%lf",&line[ i ].u.x,&line[ i ].d.x);
            line[ i ].u.y = y1;
            line[ i ].d.y = y2;
        }
        sort( line+1,line+n+1,cmp );
        line[ n+1 ].u.x = x2,line[ n+1 ].u.y = y1;
        line[ n+1 ].d.x = x2,line[ n+1 ].d.y = y2;
        memset( cnt,0,sizeof( cnt ) );
        memset( vis,0,sizeof( vis ) );
        for( int num=0;num<m;num++ ){
            point toy;
            scanf("%lf%lf",&toy.x,&toy.y);
            for( int j=0;j<=n;j++ ){
                if( xmult( toy,line[ j ].d,line[ j ].u )<-eps&&xmult( toy,line[ j+1 ].d,line[ j+1 ].u )>eps ){
                    cnt[ j ]++;
                }
            }
        }
        for( int i=0;i<=n;i++ ){
            if( cnt[ i ]!=0 )
                vis[ cnt[i] ]++;
        }
        printf("Box\n");
        for( int i=1;i<maxn;i++ ){
            if( vis[ i ]!=0 )
                printf("%d: %d\n",i,vis[ i ]);
        }
    }
    return 0;
}