poj1673EXOCENTER OF A TRIANGLE

链接

据说这题是垂心。。数学太弱没有看出来，写了分朴实无华的代码。。

旋转三边得到图中的外顶点，然后连接三角形顶点求交点，交上WA。。觉得没什么错误就去看了下discuss,发现都在说精度问题，果断开始水，最后+了epsAC了。。

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 #include<vector>
 #include<cmath>
 #include<queue>
 #include<set>
 using namespace std;
 #define N 100000
 #define LL long long
 #define INF 0xfffffff
 const double eps = 1e-;
 const double pi = acos(-1.0);
 const double inf = ~0u>>;
 struct Point
 {
     double x,y;
      Point(double x=,double y=):x(x),y(y) {}
 }p[];
 typedef Point pointt;
 pointt operator + (Point a,Point b)
 {
     return Point(a.x+b.x,a.y+b.y);
 }
 pointt operator - (Point a,Point b)
 {
     return Point(a.x-b.x,a.y-b.y);
 }
 int dcmp(double x)
 {
     if(fabs(x)<eps) return ;
     else return x<?-:;
 }
 Point rotate(Point a,double rad)
 {
     return Point(a.x*cos(rad)-a.y*sin(rad),a.x*sin(rad)+a.y*cos(rad));
 }
 bool intersection1(Point p1, Point p2, Point p3, Point p4, Point& p)      // 直线相交
 {
     double a1, b1, c1, a2, b2, c2, d;
     a1 = p1.y - p2.y;
     b1 = p2.x - p1.x;
     c1 = p1.x*p2.y - p2.x*p1.y;
     a2 = p3.y - p4.y;
     b2 = p4.x - p3.x;
     c2 = p3.x*p4.y - p4.x*p3.y;
     d = a1*b2 - a2*b1;
     if (!dcmp(d))    return false;
     p.x = (-c1*b2 + c2*b1) / d;
     p.y = (-a1*c2 + a2*c1) / d;
     return true;
 }
 double cross(Point a,Point b)
 {
     return a.x*b.y-a.y*b.x;
 }
 double mul(Point p0,Point p1,Point p2)
 {
     return cross(p1-p0,p2-p0);
 }
 int main()
 {
     int n,i;
     cin>>n;
     while(n--)
     {
         for(i = ; i <=  ; i++)
         scanf("%lf%lf",&p[i].x,&p[i].y);
         Point p1,p2,p3,p4;
         if(dcmp(mul(p[],p[],p[]))>)
         {
             p1 = rotate(p[]-p[],*pi/2.0);
             p2 = rotate(p[]-p[],pi/2.0);
         }
         else
         {
             p1 = rotate(p[]-p[],pi/2.0);
             p2 = rotate(p[]-p[],*pi/2.0);
         }
         p1.x+=p[].x;
         p1.y+=p[].y;
         p2.x+=p[].x;
         p2.y+=p[].y;
         p1.x = (p1.x+p2.x)/;
         p1.y = (p1.y+p2.y)/;

         if(dcmp(mul(p[],p[],p[]))>)
         {
             p3 = rotate(p[]-p[],*pi/2.0);
             p4 = rotate(p[]-p[],pi/2.0);
         }
         else
         {
             p3 = rotate(p[]-p[],pi/2.0);
             p4 = rotate(p[]-p[],*pi/2.0);
         }
         p3.x+=p[].x;
         p3.y+=p[].y;
         p4.x+=p[].x;
         p4.y+=p[].y;
         p3.x = (p3.x+p4.x)/;
         p3.y = (p3.y+p4.y)/;
         Point pp ;
         intersection1(p1,p[],p3,p[],pp);
         printf("%.4f %.4f\n",pp.x+eps,pp.y+eps);

     }
     return ;
 }