poj 2653 Pick

#include<cstdio>#include<algorithm>#include<cstdlib>#include<cmath>using namespace std;const int maxn =  100010;const double eps = 1e-10;struct Point{    double x,y;    Point(double x=0,double y=0):x(x),y(y) {}};typedef Point Vector;Point operator +(Vector A,Vector B){    return Vector(A.x+B.x,A.y+B.y);}Point operator -(Vector A,Vector B){    return Vector(A.x-B.x,A.y-B.y);}Point operator *(Vector A,double p){    return Vector(A.x*p,A.y*p);}Point operator /(Vector A,double p){    return Vector(A.x/p,A.y/p);}double Cross (Vector A,Vector B){    return A.x*B.y-A.y*B.x;}int dcmp(double x){    if(fabs(x)<eps)return 0;    else return x<-eps?-1:1;}double  mul(Point p0,Point p1,Point p2){    return Cross(p1-p0,p2-p1);}int cross(Point p1,Point p2,Point p3,Point p4){    double a1=mul(p1,p2,p3),a2=mul(p1,p2,p4);    if(dcmp(a1)==0&&dcmp(a2)==0)return 2;    if(dcmp(a1)==dcmp(a2))return 0;    return 1;}Point p1[maxn],p2[maxn];int n;int main(){    while(~scanf("%d",&n)&&n)    {        for(int i=0; i<n; i++)        { scanf("%lf %lf %lf %lf",&p1[i].x,&p1[i].y,&p2[i].x,&p2[i].y);        }        int f1=0;        printf("Top sticks:");        for(int i=0; i<n; i++)        { int  flag=0; for(int j=i+1; j<n; j++) {     if(cross(p1[i],p2[i],p1[j],p2[j])==1&&cross(p1[j],p2[j],p1[i],p2[i])==1)     {         flag=1;         break;     } } if(flag==0&&f1==1)printf(","); if(flag==0)printf(" %d",i+1),f1=1;        }        printf(".n");    }    return 0;}