On a 3 x 4 chessboard (see below) there are 3 black knights (B B B) and 3 white knights (W W W). Exchange knights in the minimum number of turns (hint: use graph representation).
B B B W W W
0 0 0 min # of turns 0 0 0
0 0 0 =============> 0 0 0
W W W B B B