Eight white chess knights are placed on a 3x4 chessboard, four along the top row and four along the bottom, which are labeled as P, Q, R, S, T, U, V and W, as shown in the figure.

Exchange the positions of P and T, Q and U, R and V, and S and W in minimum possible number of moves.

P	Q	R	S
T	U	V	W

Let the squares be identified from 1 through 12 being read from left to right down.

(In reply to One possible solution by Dej Mar)

Firstly:
I copied the move set offered by Dej Mar to ascertain the number of moves made by each piece:

    P  Q  R  S  T  U  V  W
    4  6   6  4  2  4  4   2

Secondly:
I notice that Q revisits the same cell twice in sets 7 and 17 and R similarly revisits a cell twice in sets  19 and 25.  Does that mean that there is still a more efficient way to exchange the pieces, or is that something that has too happen?

Edited on February 17, 2010, 7:20 pm

Posted by brianjn on 2010-02-16 21:08:19