uva 11437 - Triangle Fun
这是一道简单的计算几何；
In the picture below you can see a triangle ABC. Point D, E and F divides the sides BC, CA and AB into ratio 1:2 respectively. That is CD=2BD, AE=2CE and BF=2AF. A, D; B, E and C, F are connected. AD and BE intersects at P, BE and CF intersects at Q and CF and AD intersects at R.
So now a new triangle PQR is formed. Given triangle ABC your job is to find the area of triangle PQR.
这是我在uva上做的第一道题，纪念一下 =_=
#include<iostream>
using namespace std;
typedef struct points
{
double x,y;
points(double xx=0,double yy=0):x(xx),y(yy){}
}vectors;
points operator + (points a,vectors b)
{
return points(a.x+b.x,a.y+b.y);
}
vectors operator - (points a,points b)
{
return vectors(a.x-b.x,a.y-b.y);
}
vectors operator * (double a,vectors b)
{
return vectors(a*b.x,a*b.y);
}
double cross(vectors a,vectors b)
{
return a.x*b.y-a.y*b.x;
}
points inter(points a,points b,points c,points d)
{
vectors v=b-a,w=d-c,u=a-c;
double t=cross(w,u)/cross(v,w);
return a+t*v;
}
int main()
{
points a,b,c,d,e,f,p,q,r;
int n,area;
cin>>n;
while(n--)
{
cin>>a.x>>a.y>>b.x>>b.y>>c.x>>c.y;
d=b+1/3.0*(c-b);
e=c+1/3.0*(a-c);
f=a+1/3.0*(b-a);
p=inter(a,d,b,e);
q=inter(b,e,c,f);
r=inter(c,f,a,d);
area=(int)(0.5+cross(q-p,r-p)/2);
cout<<area<<endl;
}
return 0;
}