In the following position on a 3 x 3 chessboard, what is the minimum number of plays needed to exchange the positions of the knights (placing White knights where the Black knights currently are, and vice versa)? NB: A 'play' is not necessarily a single move; it can be successive moves by a piece, where possible.
For your answer, state the number of plays as well as the actual moves. To do this, number the squares from left to right, top to bottom. So the Black knights are currently on squares 1 and 3, and the White knights are on 7 and 9. Show your plays thus (for example): 3 - 8; 9 - 4 - 3 etc.