The Three Kings Puzzle


I had a bunch of checkers, but my checkerboard had been destroyed by a willful four year old child, and all I had left was a connected strip of three squares.

        +----+----+----+
        |    |    |    |
        |    |    |    |
        +----+----+----+
      

I decided that you can always make a game if you work at it, so I piled all my checkers into three stacks, placing one stack on each square. In regular checkers, when a piece is entitled to become a "king", a second piece is placed on top of it. In my game, I assumed that each of the three stacks was a "piece", and that each was entitled to become a king. However, a piece could only become a king if there were at least enough checkers on one of the other two square to double the size of the piece. As soon as a piece had been "kinged", it was time to identify another candidate (or even the same piece again) to be kinged once more.

For instance, here is a sequence of moves that occurred in one game:
MoveSquare 1Square 2Square 3
0 17 3 8
1 17 6 5
2 11 12 5
3 22 1 5
4 21 2 5
5 19 4 5
6 19 8 1
7 18 8 2
8 16 8 4
9 12 8 8
10 12 16 0

Since I'm making up rules as I go along, I now decide that the game is "won" if I can empty out one of the squares, that is, make one stack of checkers disappear. So in the above game, I won in 10 moves.

Can you always win this game, no matter what number of checkers are placed on each square? Is there a strategy for winning?

I give up, show me the solution.


Last revised on 25 June 2005.