模板—判断两条线段是否相交

//点的结构体
struct point
{
int x,y;
};
//叉积
TPYE 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);
}
//判断两条直线是否相交，端点重合算相交
bool IsIntersect(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)));
}