POJ1673 EXOCENTER OF A TRIANGLE（三角形垂心）

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #include <cmath>
 6 using namespace std;
 7 
 8 const double EPS = 1e-8;        //精度系数
 9 const double PI = acos(-1.0);    //π
10 
11 struct Point {
12     double x, y;
13     Point(double x = 0, double y = 0) :x(x), y(y) {}
14     const bool operator < (Point A)const {
15         return x == A.x ? y < A.y : x < A.x;
16     }
17 };    //点的定义
18 
19 typedef Point Vector;    //向量的定义
20 
21 Vector operator + (Vector A, Vector B) { return Vector(A.x + B.x, A.y + B.y); }    //向量加法
22 Vector operator - (Vector A, Vector B) { return Vector(A.x - B.x, A.y - B.y); }    //向量减法
23 Vector operator * (Vector A, double p) { return Vector(A.x*p, A.y*p); }        //向量数乘
24 
25 Vector Rotate(Vector A, double rad) {
26     return Vector(A.x*cos(rad) - A.y*sin(rad), A.x*sin(rad) + A.y*cos(rad));
27 }    //逆时针旋转rad度
28 
29 Point LineIntersectionPoint(Point A1, Point B1, Point A2, Point B2) {
30     double t1 = ((A1.y - A2.y)*(B2.x - A2.x) - (A1.x - A2.x)*(B2.y - A2.y)) /
31         ((B1.x - A1.x)*(B2.y - A2.y) - (B1.y - A1.y)*(B2.x - A2.x));
32     return A1 + (B1 - A1)*t1;
33 }    //返回直线交点
34 
35 int main() {
36     Point A, B, C;
37     int n;
38     cin >> n;
39     while (n--) {
40         scanf("%lf%lf%lf%lf%lf%lf", &A.x, &A.y, &B.x, &B.y, &C.x, &C.y);
41         Vector v = Rotate(B - A, PI / 2), u = Rotate(C - B, PI / 2);
42         Point ans = LineIntersectionPoint(C, C + v, A, A + u);
43         printf("%.4lf %.4lf\n", ans.x + EPS, ans.y + EPS);
44     }
45 }