Solving the Sudoku: Magic number turns out to be 17

Researchers have proved that the answer to the sudoku minimum number of clues problem is 17.
Gary McGuire, University College, Dublin

Puzzled by the secret of the Sudoku? You're not alone; millions of people have tried their hand at the mathematical problem-solving game since it was first popularized in 1986 in Japan. The challenge is to fill in a 9X9 grid of squares where certain cells already contain digits numbering between 1 and 9.

The idea is to fill in the remaining cells so that the rows and columns - as well as each 3×3 box - all contains all the digits numbering between 1 and 9 exactly one time.

Now Gary McGuire, a mathematician at University College Dublin, has come up with what he says is a proof that finds the minimum number of clues, or starting digits, needed to complete the game is 17. That's been a long-held assumption for quite some time. So why haven't mere mortals been able to confirm that believe? Of course, McGuire had help in the form of a supercomputer to help him in his work.

McGuire and his colleagues lay out their findings in this article they published in the online publication arXiv:1201.0749v1. You can also read a good write-up at Nature.com