W W W - B B B

6 coins are arranged in a row as above:
3 colored White and 3 colored Black,
with 1 empty space between the two sets.

Object is to reverse the positions, moving
all B's to where W's are now, and moving
all W's to where B's are now.

A coin may jump over ONLY ONE adjacent coin
to an adjacent space, or it may be moved
ONLY ONE space to an empty space.

W's can only move to the right
and B's can only move to the left.

What is the least number of moves required
to reverse the positions ?

Correct Flo.

What does your solution show, say, after 7th move?

I get 15 too.

Right!

W's = 1,2,3 ; B's = A,B,C ; empty = -

00 1 2 3 - A B C
01 1 2 3 A - B C
02 1 2 - A 3 B C
03 1 - 2 A 3 B C
04 1 A 2 - 3 B C
05 1 A 2 B 3 - C
06 1 A 2 B 3 C -
07 1 A 2 B - C 3
08 1 A - B 2 C 3
09 - A 1 B 2 C 3
10 A - 1 B 2 C 3
11 A B 1 - 2 C 3
12 A B 1 C 2 - 3
13 A B 1 C - 2 3
14 A B - C 1 2 3
15 A B C - 1 2 3