Two white and two black knights are positioned on part of a chess
board as shown.
A knight can only move in the usual way * and can only land on an empty square.
Swap the positions of the white and black knights.
Can you prove you have succeeded in the minimum number of
moves?
* A knight can move two
squares horizontally and one square vertically, or two squares
vertically and one square horizontally. The complete move therefore
looks like the letter 'L'.
Unlike all other standard chess pieces, the knight can 'jump over'
all other pieces on route to its destination square.