SudoCue Users

David Bryant · Posted: Fri Jan 27, 2006 9:16 pm Post subject: 27 Jan 2006 Nightmare

I'm not sure this is a new technique. But in the course of solving today's "Nightmare" I hit an interesting formation -- I'm not sure I've ever encountered one exactly like it before.

With 45 cells resolved and 36 still to go the puzzle looked like this (I had only made the obvious moves up to this point, plus I had used some simple coloring to eliminate one "6" [at r8c5] and one "8" [at r5c8] from the matrix).

Myth Jellies · Hooked Joined: 04 Apr 2006 Posts: 42

You can get this solution out of a nice grouped candidate chain as follows...

Ron Moore · Addict Joined: 13 Aug 2006 Posts: 72 Location: New Mexico

I just joined the forum, so I'm aware that this is very old business. I wouldn't have commented except that the solving guide states that no XYZ wing resulting in two eliminations had been discovered in practice. Well, here is one. r8c8 (pivot), r5c8, and r8c7 form the XYZ wing pattern (no need to consider column 9), which, as the previous posts have concluded, eliminates 7 from r79c8.

David Bryant · Posted: Thu Aug 17, 2006 10:45 pm Post subject: Astute observation

That's an astute observation, Ron. I'm not too good with names for some of these newer "techniques" -- I tend to rely on logic & first principles. Thanks for pointing out that this is an "XYZ-Wing" pattern.

Maybe we can get Ruud to update the solving guide. Here's an example of the double elimination XYZ-Wing in one of the early "nightmares" he published! dcb

Ruud · Site Owner Joined: 30 Dec 2005 Posts: 601

I've updated the guide. A pointer to this Nightmare has been added to the XYZ-Wing topic.

Thanks, Ron. This is the second time in a row that others have found examples I was looking for in my own puzzles.

Ruud

Ron Moore · Addict Joined: 13 Aug 2006 Posts: 72 Location: New Mexico

As it happens, while browsing through the site shortly after my post above, I came across another example which Myth Jellies points out in this post: http://sudocue.net/forum/viewtopic.php?t=194.

By the way, David, I've seen many fine posts by you and you're familiar with some techniques that are new to me.

Ron