UVA 11178 Morley's Theorem（旋转+直线交点）

Posted 2020-06-12

 

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】

 

 1 #include<cstdio>
 2 #include<cmath>
 3 #include<cstring>
 4 using namespace std;
 5 
 6 
 7 struct Pt { 
 8     double x,y;
 9     Pt(double x=0,double y=0):x(x),y(y) {}
10 };
11 typedef Pt vec;
12 
13 vec operator - (Pt A,Pt B) { return vec(A.x-B.x,A.y-B.y); }
14 vec operator + (vec A,vec B) { return vec(A.x+B.x,A.y+B.y); }
15 vec operator * (vec A,double p) { return vec(A.x*p , A.y*p); }
16 
17 double cross(vec A,vec B) { return A.x*B.y-A.y*B.x; }
18 double Dot(vec A,vec B) { return A.x*B.x+A.y*B.y; }
19 double Len(vec A) { return sqrt(Dot(A,A)); }
20 double Angle(vec A,vec B) { return acos(Dot(A,B)/Len(A)/Len(B)); }
21 
22 vec rotate(vec A,double rad) { 
23     return vec(A.x*cos(rad)-A.y*sin(rad) , A.x*sin(rad)+A.y*cos(rad));
24 }
25 Pt LineIntersection(Pt P,vec v,Pt Q,vec w) {
26     vec u=P-Q;
27     double t=cross(w,u)/cross(v,w);
28     return P+v*t;
29 }
30 Pt getD(Pt A,Pt B,Pt C) {
31     vec v1=C-B;
32     double a=Angle(A-B,v1);
33     v1=rotate(v1,a/3);
34     vec v2=B-C;
35     a=Angle(A-C,v2);
36     v2=rotate(v2,-a/3);
37     return LineIntersection(B,v1,C,v2);
38 }
39 Pt read() {
40     double x,y;
41     scanf("%lf%lf",&x,&y);
42     return Pt(x,y);
43 }
44 int main() {
45     Pt A,B,C,D,E,F;
46     int T;
47     scanf("%d",&T);
48     while(T--) {
49         A=read() , B=read() , C=read();
50         D=getD(A,B,C);
51         E=getD(B,C,A);
52         F=getD(C,A,B);
53         printf("%.6lf %.6lf %.6lf %.6lf %.6lf %.6lf\n",D.x,D.y,E.x,E.y,F.x,F.y);
54     }
55     return 0;
56 }