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Mathematician says his Sudoku secret is foolproof
Math has helped place a man on the moon and has counted the
genes in our DNA.
But never mind all that. A mathematician says he has finally
produced something that people really care about: a foolproof way to
beat Sudoku puzzles.

"Sudoku has become the passion of many people the world over,"
says computer scientist J. F. Crook of Winthrop University in Rock
Hill, S.C., in the current Notices of the American Mathematical
Society. "The interesting fact about Sudoku is that it is a trivial puzzle
to solve."
"Sudoku requires a kind of math sense," says mathematician M.
Ram Murty of Canada's Queen's University in Kingston, an expert
Sudoku provides it."

The puzzles are generally grids of 81 squares, nine across and
nine down. Some boxes have a number filled in; the rest are blank.
Players must fill in the blank squares with numbers between 1 and
9 without repeating any numbers in a row, column or the nine
interior 3-by-3 boxes of the puzzle.

Many players and strategy guides intuitively take steps like those
Crook outlines, but he says his study offers the first mathematically
guaranteed way of solving the puzzles.

Even using his method, there may be two possibilities for a
particular box. In that case, the player would have to guess which
one is right and then repeat the steps to see whether they lead to
a solution. He counsels switching pencil colors at this stage. If the
first guess doesn't work, erase and try the other option.

Murty, who has published theoretical work on Sudoku, says
Crook's steps follow well-worn mathematical approaches to
puzzles such as chess problems. "Sudoku is really just a kind of
math in action," he says.
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Sudoku has met its match: Math