Problem of the Week 1074

From a Jack to a King

Consider these red and green stones:

Label the rows, reading down, as Ten, Jack, Queen, King, Ace. Thus the red stone is a Jack.

Make it a King using a sequence of jumps that obey the following rules.

  • Any stone can jump horizontally or vertically over one or more adjacent stones into an empty space.
  • The stones that are jumped over simply stay where they are.

For example, a legal start would be: move the TEN down two squares; then the green JACK down two squares; then the rightmost ACE up three squares.

The puzzle is due to James Stephens, whose web site has a lovely collection of puzzles, especially the 12 irritating sliding block puzzles. He generates these by computer. I first saw this puzzle in the column of Joe Buhler and Elwyn Berlekamp in the MSRI Newsletter.

The actual Stephens puzzle is to get the red stone to the lower right square. But just getting it outside of the second row is not so easy.

© Copyright 2007 Stan Wagon. Reproduced with permission.

16 March 2007