poj1269

nt judgecross(){
	if(min(p[0].x,p[1].x)>max(p[2].x,p[3].x)||min(p[0].y,p[1].y)>max(p[2].y,p[3].y)||max(p[0].x,p[1].x)<min(p[2].x,p[3].x)||max(p[0].y,p[1].y)<min(p[2].y,p[3].y)){
		return 0;
	}
	double fd=compute(p[0].x-p[2].x,p[0].y-p[2].y,p[3].x-p[2].x,p[3].y-p[2].y);
	double fk=compute(p[1].x-p[2].x,p[1].y-p[2].y,p[3].x-p[2].x,p[3].y-p[2].y);
	if(fd*fk<=0){
		return 1;
	}//跨立
}  //兩線段是否相交 

void solve(){
	point intersection2(line l1, line l2)
{
    point p1 = l1.b - l1.a;
    point p2 = l2.a - l1.a;
    double d1 = fabs(across(p1, p2));
 
    point p3 = l2.b - l1.a;
    double d2 = fabs(across(p1, p3));
 
    double t = d1 / (d1 + d2);
 
    return l2.a + (l2.b - l2.a) * t;
}//兩線段交點

   if(abs((a.a-a.c)*(b.b-b.d)-(a.b-a.d)*(b.a-b.c))<inf)//判斷是否平行
        {
            if(abs((a.c-a.a)*(b.b-a.b)-(a.d-a.b)*(b.a-a.a))<inf)//判斷是否共線
               cout<<"LINE"<<endl;
            else
               cout<<"NONE"<<endl;
        }