Six chess knights are placed on a 4x3 chessboard, three along the top row and three along the bottom, which are labeled as P, Q, R, X, Y, Z, as shown in the figure below.
Exchange the positions of P and X, Q and Y and, R and Z, in minimum possible number of moves.
(In reply to Thoughts
Congratulations to Broll! I agree that you have shown 26 to be the minimum. I got the Q/Y as you did, but got entangled with the side columns. (When I copied the diagram to another paper to experiment, I numbered the columns from top to bottom, rather than bottom up -- as shown, and as you did -- so my list would be rather confusing in any case.) I considered trying to program a solution, but it seemed most likely that would get me into some infinite looping.