POJ2653 Pickup sticks

　　原题链接：http://poj.org/problem?id=2653

　　线段相交。

　　从后往前筛TLE，从前往后却AC了，数据坑爹。

#include <cstdio>
#define maxn 100005
const double eps = 1e-8;
struct segment
{
    double x1, y1, x2, y2;
}seg[maxn];

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

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

bool segcross(segment seg1, segment seg2)
{
    if(min(seg1.x1, seg1.x2) > max(seg2.x1, seg2.x2) ||
       min(seg1.y1, seg1.y2) > max(seg2.y1, seg2.y2) ||
       min(seg2.x1, seg2.x2) > max(seg1.x1, seg2.x2) ||
       min(seg2.y1, seg2.y2) > max(seg1.y1, seg2.y2)) return 0;

    double h, i, j, k;
    h = (seg1.x2 - seg1.x1) * (seg2.y1 - seg1.y1) - (seg1.y2 - seg1.y1) * (seg2.x1 - seg1.x1);
    i = (seg1.x2 - seg1.x1) * (seg2.y2 - seg1.y1) - (seg1.y2 - seg1.y1) * (seg2.x2 - seg1.x1);
    j = (seg2.x2 - seg2.x1) * (seg1.y1 - seg2.y1) - (seg2.y2 - seg2.y1) * (seg1.x1 - seg2.x1);
    k = (seg2.x2 - seg2.x1) * (seg1.y2 - seg2.y1) - (seg2.y2 - seg2.y1) * (seg1.x2 - seg2.x1);
    return h * i < eps && j * k < eps;
}

int main()
{
    int n, i, j, stick[1005], cnt;
    bool flag;
    while(scanf("%d", &n), n)
    {
        for(i = 0; i < n; i ++)
            scanf("%lf%lf%lf%lf", &seg[i].x1, &seg[i].y1, &seg[i].x2, &seg[i].y2);

        cnt = 0;

        for(i = 0; i < n; i ++)
        {
            flag = false;
            for(j = i + 1; j < n; j ++)
            {
                if(segcross(seg[i], seg[j]))
                {
                    flag = true;
                    break;
                }
            }
            if(!flag)
                stick[++ cnt] =  i + 1;
        }
        printf("Top sticks:");
        for(i = 1; i < cnt; i ++)
        {
            printf(" %d,", stick[i]);
        }
        printf(" %d.\n", stick[i]);
    }
    return 0;
}