POJ 2653 Pick-up sticks 枚举 + 判断两线段规范相交

 有技巧的暴力过了

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
using namespace std;
#define eps 10e-8
#define inf 1<<29
struct point
{
    double x, y;
};
struct seg
{
    point a, b;
}s[100002];

bool vis[100003];
int ans[100003];
int n;

double cross(point p0, point p1, point p2)
{
    return (p1.x - p0.x)*(p2.y - p0.y) - (p1.y - p0.y)*(p2.x - p0.x);
}
bool line_cross(seg s1, seg s2)//判断两线段是否规范相交
{
      if(cross(s1.a, s1.b, s2.a)*cross(s1.a, s1.b, s2.b) > -eps
      || cross(s2.a, s2.b, s1.a)*cross(s2.a, s2.b, s1.b) > -eps
      )return 0;
    return 1;
}
int main()
{
    int i, j;
    while(~scanf("%d",&n) && n)
    {
        for(i=1;i<=n;i++)
            scanf("%lf%lf%lf%lf", &s[i].a.x, &s[i].a.y, &s[i].b.x, &s[i].b.y);
        memset(vis, 0, sizeof(vis));
        for(i=1;i<=n;i++)
            for(j=i+1;j<=n;j++)
                if(line_cross(s[i], s[j])){vis[i]=1;break;}//用break就不会超时    
        printf("Top sticks: ");
        int num = 0 ;
        for(i=1;i<=n;i++)
            if(!vis[i])
                ans[num++]=i;
        for(i=0;i<num-1;i++)
            printf("%d, ",ans[i]);
        printf("%d.\n",ans[i]);
    }
    return 0;
}