POJ 1329 Circle Through Three Points(三角形外心)

题目链接

抄的外心模版。然后，输出认真一点。1Y。

 #include <cstdio>
 #include <cstring>
 #include <string>
 #include <cmath>
 #include <algorithm>
 using namespace std;
 #define eps 1e-8
 struct point
 {
     double x,y;
 };
 struct line
 {
     point a,b;
 };
 point intersection(line u,line v)
 {
     point ret = u.a;
     double t = ((u.a.x-v.a.x)*(v.a.y-v.b.y)-(u.a.y-v.a.y)*(v.a.x-v.b.x))
     /((u.a.x-u.b.x)*(v.a.y-v.b.y)-(u.a.y-u.b.y)*(v.a.x-v.b.x));
     ret.x += (u.b.x-u.a.x)*t;
     ret.y += (u.b.y-u.a.y)*t;
     return ret;
 }
 point circumcenter(point a,point b,point c)
 {
     line u,v;
     u.a.x = (a.x+b.x)/;
     u.a.y = (a.y+b.y)/;
     u.b.x = u.a.x - a.y + b.y;
     u.b.y = u.a.y + a.x - b.x;
     v.a.x = (a.x+c.x)/;
     v.a.y = (a.y+c.y)/;
     v.b.x = v.a.x - a.y + c.y;
     v.b.y = v.a.y + a.x - c.x;
     return intersection(u,v);
 }
 double dis(point p1,point p2)
 {
     return sqrt((p1.x-p2.x)*(p1.x-p2.x) + (p1.y-p2.y)*(p1.y-p2.y));
 }
 int main()
 {
     point p1,p2,p3,cr;
     double r,c,d,e;
     while(scanf("%lf%lf",&p1.x,&p1.y)!=EOF)
     {
         scanf("%lf%lf",&p2.x,&p2.y);
         scanf("%lf%lf",&p3.x,&p3.y);
         cr = circumcenter(p1,p2,p3);
         r = dis(cr,p1);
         cr.x = -cr.x;
         cr.y = -cr.y;
         if(cr.x > -eps)
         printf("(x + %.3f)^2",cr.x+eps);
         else
         printf("(x - %.3f)^2",-(cr.x+eps));
         if(cr.y > -eps)
         printf(" + (y + %.3lf)^2 = ",cr.y+eps);
         else
         printf(" + (y - %.3lf)^2 = ",-(cr.y+eps));
         printf("%.3lf^2\n",r+eps);
         c = cr.x*;
         d = cr.y*;
         e = cr.x*cr.x + cr.y*cr.y - r*r;
         printf("x^2 + y^2 ");
         if(c > -eps)
         printf("+ %.3fx ",c+eps);
         else
         printf("- %.3fx ",-(c+eps));
         if(d > -eps)
         printf("+ %.3fy ",d+eps);
         else
         printf("- %.3fy ",-(d+eps));
         if(e > -eps)
         printf("+ %.3f = 0\n\n",e+eps);
         else
         printf("- %.3f = 0\n\n",-(e+eps));
     }
 }