Here’s another little chess puzzle by Martin Gardner, taken from the same paper as earlier.
The task is to place two rooks, two bishops, and two knights on a 4 by 4 chessboard so that no piece attacks any other.
As before, there are two basic solutions, plus symmetries.
See this post for solutions, and a Prolog program that finds and enumerates the solutions.
The bishops are on the same coloured squares in both solutions though. Whilst that could come about it still feels like a bit of a cheat.