poj 1269 计算几何

 /**
 判断直线位置关系
 **/
 #include <iostream>
 #include <cmath>
 #include <cstdio>
 using namespace std;
 struct point {
     double x,y;
     point(double x=,double y=):x(x),y(y){}
 };

 typedef point Vector;

 Vector operator - (point A,point B){
     return Vector(A.x-B.x,A.y-B.y);
 }

 struct line {
     point a,b;
 };
 double length(Vector v){
     return sqrt(v.x*v.x+v.y*v.y);
 }

 double  cross(Vector A,Vector B){
     return A.x*B.y-A.y*B.x;
 }

 double distoline(point P,point A,point B){
     Vector v1 =B-A,v2 = P-A;
     return fabs(cross(v1,v2))/length(v1);
 }

 int main()
 {
     int n;
     cin>>n;
     line l1,l2;
     cout<<"INTERSECTING LINES OUTPUT"<<endl;
     while(n--){
         cin>>l1.a.x>>l1.a.y>>l1.b.x>>l1.b.y;
         cin>>l2.a.x>>l2.a.y>>l2.b.x>>l2.b.y;
         Vector tmp1,tmp2;
         tmp1.x = l1.b.x-l1.a.x;
         tmp1.y = l1.b.y-l1.a.y;
         tmp2.x = l2.b.x-l2.a.x;
         tmp2.y = l2.b.y-l2.a.y;
         //cout<<tmp1.x<<" "<<tmp1.y<<endl;
         //cout<<tmp2.x<<" "<<tmp2.y<<endl;
         //cout<<cross(tmp1,tmp2)<<endl;
         if(cross(tmp1,tmp2)==){
             if(distoline(l1.a,l2.a,l2.b)==){
                 cout<<"LINE"<<endl;
             }else
                 cout<<"NONE"<<endl;
         }else{
             double x,y;
             if(l1.a.x==l1.b.x&&l2.a.x!=l2.b.x){
                 x = l1.a.x;
                 double k = (l2.b.y-l2.a.y)/(l2.b.x-l2.a.x);
                 double b = l2.a.y-k*l2.a.x;;
                 y = k*x+b;
             }else if(l1.a.x!=l1.b.x&&l2.a.x==l2.b.x){
                 x = l2.a.x;
                 double k = (l1.b.y-l1.a.y)/(l1.b.x-l1.a.x);
                 double b = l1.a.y-k*l1.a.x;
                 y = k*x+b;
             }else{
                 double k1= (l1.b.y-l1.a.y)/(l1.b.x-l1.a.x);
                 double b1=l1.a.y-k1*l1.a.x;
                 double k2 = (l2.b.y-l2.a.y)/(l2.b.x-l2.a.x);
                 double b2=l2.a.y-k2*l2.a.x;
                 x =(b2-b1)/(k1-k2);
                 y = k1*x+b1;
             }

             printf("POINT %.2lf %.2lf\n",x,y);
         }
     }
     cout<<"END OF OUTPUT"<<endl;
     return ;
 }