A Sudoku with NO numbers provided whatsoever? Devious and/or fiendishly clever? One solution from millions? Yes!



The rules here are really very simple!
It's a basic Sudoku with 1 to 9 appearing in every row, column and each of the nine blocks, although not diagonally (no large 'X'). All numbers that are higher than their abutting non-diagonal cell neighbours in the same block are in the pink cells. All numbers that are lower than their abutting (non-diagonal) cell neighbours in each block are in the blue cells. (The colour relationships do not apply between adjacent blocks!!)

That's it! Definitely enough to get any self-respecting hard-core Sudoku fanatic started with a combination of some logical thinking and standard Sudoku techniques.

Note: Graphic is a "jpg", xhtml generated by brianjn.

It looks like there are two solutions:

512973648
367824195
498615372
759432861
281569437
643781259
836257914
925146783
174398526

The bolded 5s and 6s can be switched, and since no two are adjacent all relative orders are the same.

I used Mathematica to interactively determine the candidates for each square, and solved it in a modified version of sgt-puzzle's Solo: every time I got new information in one program I used it to try to get new information using the other.  But I had to guess once at the end, and each choice led to one solution.

Posted by Eigenray on 2009-02-13 08:44:29