UVA 11178 Morley's Theorem（旋转+直线交点）

题目链接：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=18543

【思路】

旋转+直线交点

第一个计算几何题，照着书上代码打的。

【代码】

 #include<cstdio>
 #include<cmath>
 #include<cstring>
 using namespace std;

 struct Pt {
     double x,y;
     Pt(double x=,double y=):x(x),y(y) {}
 };
 typedef Pt vec;

 vec operator - (Pt A,Pt B) { return vec(A.x-B.x,A.y-B.y); }
 vec operator + (vec A,vec B) { return vec(A.x+B.x,A.y+B.y); }
 vec operator * (vec A,double p) { return vec(A.x*p , A.y*p); }

 double cross(vec A,vec B) { return A.x*B.y-A.y*B.x; }
 double Dot(vec A,vec B) { return A.x*B.x+A.y*B.y; }
 double Len(vec A) { return sqrt(Dot(A,A)); }
 double Angle(vec A,vec B) { return acos(Dot(A,B)/Len(A)/Len(B)); }

 vec rotate(vec A,double rad) {
     return vec(A.x*cos(rad)-A.y*sin(rad) , A.x*sin(rad)+A.y*cos(rad));
 }
 Pt LineIntersection(Pt P,vec v,Pt Q,vec w) {
     vec u=P-Q;
     double t=cross(w,u)/cross(v,w);
     return P+v*t;
 }
 Pt getD(Pt A,Pt B,Pt C) {
     vec v1=C-B;
     double a=Angle(A-B,v1);
     v1=rotate(v1,a/);
     vec v2=B-C;
     a=Angle(A-C,v2);
     v2=rotate(v2,-a/);
     return LineIntersection(B,v1,C,v2);
 }
 Pt read() {
     double x,y;
     scanf("%lf%lf",&x,&y);
     return Pt(x,y);
 }
 int main() {
     Pt A,B,C,D,E,F;
     int T;
     scanf("%d",&T);
     while(T--) {
         A=read() , B=read() , C=read();
         D=getD(A,B,C);
         E=getD(B,C,A);
         F=getD(C,A,B);
         printf("%.6lf %.6lf %.6lf %.6lf %.6lf %.6lf\n",D.x,D.y,E.x,E.y,F.x,F.y);
     }
     return ;
 }