两线段是否相交模板

#include<bits/stdc++.h>
using namespace std;
struct point
{
    int x,y;
}p1,p2,p3,p4;
int cross(const point &a,const point &b,const point &o)
{
    return (a.x-o.x)*(b.y-o.y)-(b.x-o.x)*(a.y-o.y);
}
bool work(const point &a,const point &b,const point &c,const point &d)
{
    return ((cross(a,d,c)*cross(d,b,c)>=0)&&(cross(c,b,a)*cross(b,d,a)>=0)
            &&(max(c.x,d.x)>=min(a.x,b.x))&&(max(a.x,b.x)>=min(c.x,d.x))
            &&(max(c.y,d.y)>=min(a.y,b.y))&&(max(a.y,b.y)>=min(c.y,d.y)));
}
int main()
{
    while(scanf("%d%d%d%d%d%d%d%d",&p1.x,&p1.y,&p2.x,&p2.y,&p3.x,&p3.y,&p4.x,&p4.y)!=EOF)
    {
        if(work(p1,p2,p3,p4)) puts("YES");
        else puts("NO");
    }
    return 0;
}