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002 15 puzzle

15 puzzle

The history of the 15 puzzle.

In 1878 Sam Loyd, America's greatest puzzle-expert, "drove the whole world crazy" with his newly "discovered" 14-15 puzzle. This was a variation on the The Puzzle 15 which was made and sold by the Embossing Company from New York about 10 years earlier. This puzzle consisted of 15 numbered square pieces that could be slided around in a square box that was big enough to contain 16 pieces. The pieces should be placed at random in the box and you should sort the pieces in ascending order without taking the pieces out of the box (so the only thing that is allowed is to slide the pieces). Not every randomly placed pattern of pieces can be sorted by just shuffling and Sam Loyd cleverly made use of this fact.

It was not surprising that Sam drove the whole world crazy by his variation of the puzzle of 15. The problem that he formulated was impossible to solve. When you bought Sam's 14-15 puzzle the empty square was positioned bottom right. The pieces were numbered in order from left to right and from top to bottom; only the pieces numbered 14 and 15 were reversed. You should re-order the pieces so all the pieces are in the correct position and the empty place should be positioned bottom right again. For the correct solution a prize of 1000 dollar was offered but Sam kept that money in his pocket. A slide puzzle with square pieces can only be solved when the number of exchanges necessary to solve the puzzle is even. The 14-15 puzzle attracted a world wide attention that can only be compared with the Rubik's Cube that conquered the world 100 years later.   Ernö Rubik was in fact inspired by the slide puzzle when he designed his famous cube.