poj 2653 Pick-up sticks

额，看不懂题意，我以为是求一个凸壳之类的东西。。瞬间就吓虚了。。

其实就是搞一个和后面的线段没有交点就行。。。23333

而且还是随便暴力，，，，，2333扒了一发题解压压惊2333

#include<cstdio>
#include<cstring>
#include<cmath>
#define N 100005
#define inf 0x3f3f3f3f
#define eps 1e-8
using namespace std;
int ans[N],cnt,n;
bool cov[N];
struct point{double x,y;};
struct line{point a,b;}a[N];
point vec(point a, point b)
{
    point t; t.x=a.x-b.x; t.y=a.y-b.y; return t;
}
double cross(point a, point b)
{
    return a.x*b.y-a.y*b.x;
}
double turn(point p1, point p2, point x)
{
    return cross(vec(x,p1),vec(p2,p1));
}
bool cover(int i, int j)
{
    if (turn(a[i].a,a[i].b,a[j].a)*turn(a[i].a,a[i].b,a[j].b)>0) return 0;
    if (turn(a[j].a,a[j].b,a[i].a)*turn(a[j].a,a[j].b,a[i].b)>0) return 0;
    return 1;
}
void solve()
{
    printf("Top sticks: "); cnt=0;
    for (int i=1; i<=n; i++)
    {
        bool flag=0;
        for (int j=i+1; j<=n; j++)
        {
            if (cover(i,j)) {flag=1; break;}
        }
        if (!flag) ans[++cnt]=i;
    }
    for (int i=1; i<cnt; i++) printf("%d, ",ans[i]);
    printf("%d",ans[cnt]);
    puts(".");
}
int main()
{
    while (scanf("%d",&n) && n)
    {
        for (int i=1; i<=n; i++)
            scanf("%lf%lf%lf%lf",&a[i].a.x,&a[i].a.y,&a[i].b.x,&a[i].b.y);
        solve();
    }
    return 0;
}