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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."

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.

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.

Sudoku has met its match: Math