The 15-puzzle was a version of a
sliding puzzle (or sliding piece puzzle) invented by Noyes Palmer Chapman,
possibly as early as 1874. The puzzle is
played by mixing up the number arrangement and then try to move the blocks
(without removing them from the box – only by sliding them around) to rearrange
the numbers in order from 1 to 15, as shown below.
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The 15-puzzle was a version of a
sliding puzzle (or sliding piece puzzle) invented by Noyes Palmer Chapman,
possibly as early as 1874. The puzzle is
played by mixing up the number arrangement and then try to move the blocks
(without removing them from the box – only by sliding them around) to rearrange
the numbers in order from 1 to 15, as shown below.
Sam Loyd (a chess player and puzzlist)
claimed from 1891 until his death in 1911 that he had invented the puzzle. This dispute, however, is not the big story
behind this puzzle.
Sam Loyd offered a new challenge. He offered a version of this puzzle with the
14 and 15 switched (see below), and he offered a $1000 prize to anybody who
could provide a written solution for this puzzle. Many people accepted the challenge, and a few
did submit “solutions” trying to obtain the $1000 prize, but no one was able to
submit a correct solution. This is
because this puzzle, in this configuration, is impossible to solve.
The solution to this problem depends on
“parity” – in short there is an even and an odd version of this puzzle. Swapping the 14 and 15 changes the parity and
makes the problem unsolvable.
Modern versions of this puzzle are
usually construct of plastic pieces that have slots and grooves along the sides
of the pieces that make in impossible (or almost impossible) to remove the
pieces. It is impossible to change the
parity of these puzzles without removing the pieces. In other words you can’t arrange the pieces
to swap the 14 and 15 blocks, and leave the rest of the blocks in the correct
order.
REFERENCES:
David
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