Sudoku warning

[Rocker]

I have to warn my fellow woodworkers that Sudoku, see http://www.sudoku.com , can be seriously addictive. So, if you value your shed time, don't go there; you could easily find yourself wasting an hour or two per day on it. However, for those of us who, like myself and, recently, Bitingmidge, are over the hill, it could be valuable as anti-Alzheimer's therapy

Rocker

[ndru]

Too late, already been bitten. Its now my daily lunctime ritual!

This is a good source for daily puzzles.

There is a solver available at http://www.di-mgt.com.au/sudoku.html in MS Excel form if you get really stumped.

[Rocker]

ndru,
I have bought (for US$15) the Sudoku generating program that enables you to generate puzzles of whatever level of difficulty you prefer. I try to do at least one 'very hard' one daily. The secret of their solution is to use the pairs, trios, quartos, and quints principle, which is just an extension of the pairs principle.

Rocker

[ndru]

I try to do at least one 'very hard' one daily. Rocker

I wish I had the time to do that, too!

I recently came across this useful "solver", which operates more like a tutor.

http://www.scanraid.com/sudoku.htm

[zathras]

I travelled overseas for work recently.
I printed off a stack of sudoku puzzles from the internet in advance. These came in useful as very effective timewasters.

Certainly beats staring around a plane in total boredom

It is amazing how some puzzles can be so simple, yet some are so devilish.

[Rocker]

ndru,

Thanks for that link. It points out a number of strategies that I wasn't aware of. I think I have grasped 'pointing pairs' and 'box-line reduction', but I still need to work on 'X-wing', 'Swordfish' and 'hidden pairs'.

I was surprised, though, that the site does not extend the pairs strategy referred to in Step 4 to include triplets, quadruplets and quintuplets. Actually the Belgian site that he links to for the X-wing strategy does state this strategy in rather obscure terms, calling it 'disjoint subsets':

"When N cells, in a unit, have only N candidates between them, those N candidates may be eliminated from the other cells in the unit."

Thus, if, say 3, cells in a row, column, or box, have only 3 candidates between them, then those 3 candidates can be eliminated from the other cells in the row, column, or box. e.g., if the three cells contain the candidates 2-4, 3-4, and 2-3-4, then 2,3, and 4 can be eliminated from the other cells in the row, column, or box. And similarly for larger numbers of cells/candidates.

Rocker