11
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In a sudoku puzzle, what is the absolute minimum number of clues that must be given to specify a layout with a unique solution? Is one in each row, column, and box (9 total) necessary or sufficient?

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17
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For a standard $9 \times 9$ sudoku, the minimum is $17$ squares. It had long been known that at least $16$ were required and that $17$ was sufficient. This article closes the gap.

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