uva 11178

计算几何

边的旋转、直线相交的应用

代码：

#include<cstdio>
#include<cmath>
using namespace std;
struct node
{
    double x,y;
    node(double x=0,double y=0):x(x),y(y){}
}a,b,c,d,e,f;
 node operator-(node u,node v){return node(u.x-v.x,u.y-v.y);}
 node operator+(node u,node v){return node(u.x+v.x,u.y+v.y);}
 node operator*(node u,double v){return node(u.x*v,u.y*v);}
 node operator/(node u,double v){return node(u.x/v,u.y/v);}

double cross(node u,node v)
{
    return u.x*v.y-u.y*v.x;
}

node rotate(node a,double rad)
{
    return node(a.x*cos(rad)-a.y*sin(rad),a.x*sin(rad)+a.y*cos(rad));
}

double dot(node a,node b)
{
    return a.x*b.x+a.y*b.y;
}

double length(node a)
{
    return sqrt(dot(a,a));
}

double angle(node a,node b)
{
    return acos(dot(a,b)/length(a)/length(b));
}

node getnode(node p,node v,node q,node w)
{
     node u=p-q;
     double t=cross(w,u)/cross(v,w);
     return p+v*t;
}

node get(node a,node b,node c)
{
    node v1=c-b;
    double a1=angle(a-b,v1);
    v1=rotate(v1,a1/3);
    node v2=b-c;
    double a2=angle(a-c,v2);
    v2=rotate(v2,-a2/3);
    return getnode(b,v1,c,v2);
}
int main()
{
    int n;
    scanf("%d",&n);
    while(n--)
    {
        scanf("%lf%lf",&a.x,&a.y);
        scanf("%lf%lf",&b.x,&b.y);
        scanf("%lf%lf",&c.x,&c.y);
        d=get(a,b,c);
        e=get(b,c,a);
        f=get(c,a,b);
        printf("%.6lf %.6lf ",d.x,d.y);
        printf("%.6lf %.6lf ",e.x,e.y);
        printf("%.6lf %.6lf
",f.x,f.y);
    }
    return 0;
}