Pick-up Sticks

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Stan has n sticks of various length. He throws them one at a time on the floor in a random way. After finishing throwing, Stan tries to find the top sticks, that is these sticks such that there is no stick on top of them. Stan has noticed that the last thrown stick is always on top but he wants to know all the sticks that are on top. Stan sticks are very, very thin such that their thickness can be neglected.

Input

Input consists of a number of cases. The data for each case start with 1 ≤ n ≤ 100000, the number of sticks for this case. The followingn lines contain four numbers each, these numbers are the planar coordinates of the endpoints of one stick. The sticks are listed in the order in which Stan has thrown them. You may assume that there are no more than 1000 top sticks. The input is ended by the case with n=0. This case should not be processed.

Output

For each input case, print one line of output listing the top sticks in the format given in the sample. The top sticks should be listed in order in which they were thrown.

The picture to the right below illustrates the first case from input.

Sample Input

51 1 4 22 3 3 11 -2.0 8 41 4 8 23 3 6 -2.030 0 1 11 0 2 12 0 3 10

Sample Output

Top sticks: 2, 4, 5.Top sticks: 1, 2, 3.

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY
从前向后判断第i是否和第j根线段相交，分为点在线上和线在线上，如果只是端点与端点重合而线段不重合，则继续，否则break；此外，线段相交；也要break；

#include<stdio.h>#include<string.h>#include<iostream>using namespace std;double MAX(double a,double b){return a>b?a:b;}double MIN(double a,double b){return a<b?a:b;}struct point{double x,y;};struct line{point a,b;}p[100008];double cross(point a,point b,point c){return (c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);}int onsegment(point a,point b,point c){double d1=MIN(a.x,b.x);double d2=MAX(a.x,b.x);double d3=MIN(a.y,b.y);double d4=MAX(a.y,b.y);if(d1<=c.x&&c.x<=d2&&d3<=c.y&&c.y<=d4)return 1;return 0;}int segment(point a,point b,point c,point d){double d1=cross(c,d,a);double d2=cross(c,d,b);double d3=cross(a,b,c);double d4=cross(a,b,d);if(d1*d2<0&&d3*d4<0)return 1;else if(d1==0&&onsegment(c,d,a))return 1;else if(d2==0&&onsegment(c,d,b))return 1;else if(d3==0&&onsegment(a,b,c))return 1;else if(d4==0&&onsegment(a,b,d))return 1;return 0;}int g[100008];int main(){int i,j,k,m,n;while(scanf("%d",&m),m){for(i=0;i<m;i++)scanf("%lf%lf%lf%lf",&p[i].a.x,&p[i].a.y,&p[i].b.x,&p[i].b.y);n=0;for(i=0;i<m;i++){for(j=i+1;j<m;j++){if(segment(p[i].a,p[i].b,p[j].a,p[j].b)){if((p[i].a.x!=p[j].a.x||p[i].a.y!=p[j].a.y)&&(p[i].b.x!=p[j].a.x||p[i].b.y!=p[j].a.y)&&(p[i].a.x!=p[j].b.x||p[i].a.y!=p[j].b.y)&&(p[i].b.x!=p[j].b.x||p[i].b.y!=p[j].b.y)){break;}else{if((onsegment(p[i].a,p[i].b,p[j].a)&&onsegment(p[i].a,p[i].b,p[j].b))||(onsegment(p[j].a,p[j].b,p[i].a)&&onsegment(p[j].a,p[j].b,p[i].b)))break;elsecontinue;}}}if(j==m){g[n++]=i+1;}}printf("Top sticks:");for(i=0;i<n-1;i++){printf(" %d,",g[i]);}printf(" %d.\n",g[n-1]);}return 0;}