Problem Description
Given four points ABCD, if ABCD is a tetrahedron, calculate the inscribed sphere of ABCD.
Input
Multiple test cases (test cases ≤100).
Each test cases contains a line of 12 integers [−1e6,1e6] indicate the coordinates of four vertices of ABCD.
Input ends by EOF.
Output
Print the coordinate of the center of the sphere and the radius, rounded to 4 decimal places.
If there is no such sphere, output "O O O O".
Sample Input
0 0 0 2 0 0 0 0 2 0 2 0
0 0 0 2 0 0 3 0 0 4 0 0
Sample Output
0.4226 0.4226 0.4226 0.4226
O O O O
https://blog.csdn.net/shannonnansen/article/details/51970314