poj 2653 计算几何

#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cstdio>
using namespace std;
struct  point {
    double x,y;
};
point be[100005],en[100005];
int ans[100005];
int res[100005];

double max(double a,double b){
    return a>b?a:b;
}
double min(double a,double b){
    return a<b?a:b;
}

int inter(point a,point b,point c,point d){
    if(min(a.x,b.x)>max(c.x,d.x)||min(a.y,b.y)>max(c.y,d.y)||min(c.x,d.x)>max(a.x,b.x)||min(c.y,d.y)>max(a.y,b.y))
        return 0;
    double h,i,j,k;
    h = (c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);
    i = (d.x-a.x)*(b.y-a.y)-(d.y-a.y)*(b.x-a.x);
    j = (a.x-c.x)*(d.y-c.y)-(a.y-c.y)*(d.x-c.x);
    k = (b.x-c.x)*(d.y-c.y)-(b.y-c.y)*(d.x-c.x);
    return h*i<0&&j*k<0;
}
int main()
{
    int n;
    while(scanf("%d",&n)==1&&n){
        for(int i=0;i<n;i++)
            cin>>be[i].x>>be[i].y>>en[i].x>>en[i].y;
        memset(ans,0,sizeof(ans));
        memset(res,0,sizeof(res));
        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                if(inter(be[i],en[i],be[j],en[j])){
                    ans[i] =1;
                    break;
                }
            }
        }
        int cnt =0;
        for(int i=0;i<n;i++){
            if(!ans[i])
                res[cnt++] = i+1;
        }
        printf("Top sticks: ");
        for(int i=0;i<cnt-1;i++)
            printf("%d, ",res[i]);
        printf("%d.
",res[cnt-1]);

    }
    return 0;
}