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AZ Matt · Posted: Wed Jul 19, 2006 6:43 pm Post subject: BUG Removal Theory Question

In order to use a rule, I have to understand why it works (to "see" it), and it appears I need some help with BUG removal.

I have read Jeff's and Myth Jellie's posts from the archives here from back when this must have been a hot topic, but I am still not sure I "see" it.

Is it that for the lone three candidate cell, the correct answer must create (at least ?) a three candidate subset in the column and row because if it created a matched pair there would be what I would call a "balance" to the puzzle (i.e., there would be more than one solution).

I think I see that, but I could be way off base here.

TKiel · Joined: 22 Feb 2006 Posts: 292 Location: Kalamazoo, MI

My understanding is that the three-candidate cell must be the value that appears three times in the row, column or box or else the puzzle would have multiple solutions, which makes it a bit like a unique rectangle without the rectangle part. So I think your concept of a balance equating to more than one solution would be correct.

David Bryant · Joined: 29 Jul 2005 Posts: 559 Location: Denver, Colorado

You have it exactly right, Matt. The rather fanciful title Bivalue Universal Grave is supposed to indicate that if the network of values remaining to be resolved consists entirely of matched pairs, then we can "bury" the puzzle, because two different solutions would be possible. So the "BUG + 1" technique is just a more complex version of the "unique rectangle" that has been kicked around so thoroughly. dcb Smile

AZ Matt · Posted: Wed Jul 19, 2006 11:52 pm Post subject: Thanks

Thanks TKiel and David. It makes perfect sense now that I look at it. I was struggling with a puzzle that had a bunch of two-candidate naked triples and quads, so it was not as easy to see as with a bunch of matched pairs -- no matter how big the sets, if every number can only fit twice in any row, column, or box, you have two possible solutions.

ravel · Joined: 21 Apr 2006 Posts: 536

To be more precise, such a BUG pattern either has multiple solutions or none.

For a sample look at this one (xy-wing before BUG)

fanya · Joined: 24 Jul 2006 Posts: 8

Sorry to be a pest, but...

Could someone please explain what a BUG is? Or Matt, give a pointer to where you found the archived discussion of Jeff's and Myth Jellie's?

I'm having trouble keeping track of where all the terminology is written.

The issue of terminology is relevant to the hint question in the Daily Sudoku discussion on adding a feature to the player to explain hints. If we don't have a good faq where the techniques are explained, you're likely to get more questions.

If I'm not mistaken, I've noticed that the faq deals only with site questions, not playing techniques.

Fanya
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[URL=http://www.dodge-wiki.com/wiki/Chrysler_Pacifica_(1999_concept_vehicle)]Chrysler Pacifica (1999 concept vehicle) specifications[/URL]

David Bryant · Joined: 29 Jul 2005 Posts: 559 Location: Denver, Colorado

Hi again, fanya!

The BrainBashers web site has a pretty good description of the "BUG" pattern, and how it works.

For more about terminology and playing techniques, try looking at the ScanRaid web site, and also at Ruud's "Nightmare" web site. dcb

fanya · Joined: 24 Jul 2006 Posts: 8

Thanks DB! These pointers were very helpful. One could spend a lifetime on these finer points.

Fanya
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