1 #include <iostream>
2 #include <cstdio>
3 #include <cstring>
4 #include <cmath>
5 #include <cstdlib>
6 #include <algorithm>
7 #include <vector>
8 #include <stack>
9 #include <queue>
10 #include <cassert>
11 #include <
set>
12 #include <sstream>
13 #include <map>
14 using namespace std ;
15 #ifdef DeBUG
16 #define bug assert
17 #else
18 #define bug
//
19 #endif
20 #define zero {0}
21 #define INF 2000000000
22 #define EPS 1e-10
23 inline
int sgn(
double x)
//sgn函数符号判断 ，小于给定精度判零
24 {
25 return fabs(x) < EPS ?
0 :(x <
0 ? -
1 :
1);
26 }
27 struct POINT
28 {
29 double x;
30 double y;
31 POINT()
32 {
33 }
34 POINT(
double a,
double b):x(a),y(b)
35 {
36 }
37 };
38 double dist(POINT p,POINT r)
39 {
40 return sqrt((p.x-r.x)*(p.x-r.x)+(p.y-r.y)*(p.y-
r.y));
41 }
42 bool cocircle(POINT p1,POINT p2,POINT p3,POINT &q,
double &
r)
43 {
44 double x12=p2.x-
p1.x;
45 double y12=p2.y-
p1.y;
46 double x13=p3.x-
p1.x;
47 double y13=p3.y-
p1.y;
48 double z2=x12*(p1.x+p2.x)+y12*(p1.y+
p2.y);
49 double z3=x13*(p1.x+p3.x)+y13*(p1.y+
p3.y);
50 double d=
2.0*(x12*(p3.y-p2.y)-y12*(p3.x-
p2.x));
51 if(abs(d)<EPS)
//共线，圆不存在
52 return false;
53 q.x=(y13*z2-y12*z3)/
d;
54 q.y=(x12*z3-x13*z2)/
d;
55 r=
dist(p1,q);
56 return true;
57 }
58 int main()
59 {
60 #ifdef DeBUGn
61
62 freopen(
"C:\\Users\\Sky\\Desktop\\1.in",
"r",stdin);
63 #endif
64 int T;
65 double x1,x2,x3,y1,y2,y3;
66 scanf(
"%d",&
T);
67 while(T--
)
68 {
69 POINT xin;
70 double r;
71 cin>>x1>>y1>>x2>>y2>>x3>>
y3;
72 /*
73 if(sgn((x3-x1)*(y2-y1)-(y3-y1)*(x2-x1))==0)
74 printf("No this position\n");
75 else
76 {*/
77 if(cocircle(POINT(x1,y1),POINT(x2,y2),POINT(x3,y3),xin,r))
78 printf(
"%.1lf %.1lf\n",xin.x,xin.y);
79 else if((x1==x2&&y1==y2)||(x1==x3&&y1==y3)||(x2==x3&&y2==y3))
//知道数据了这里偷个懒呵呵，应判断两点中点
80 printf(
"%.1lf %.1lf\n",(x1+x2+x3)/
2,(y1+y2+y3)/
2);
81 else
82 printf(
"No this position\n");
83 //}
84 }
85 return 0;
86 }
View Code
转载于:https://www.cnblogs.com/Skyxj/p/3227904.html
相关资源：数据结构—成绩单生成器
