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I'm trying to implement this (after successfully implementing ALS-XZ), but am confused by the fact that the preconditions mention digits Y and Z, but make no use of them later on. Are they not important? If so, perhaps the preconditions should read "A and C share a restricted common, and B and C share a restricted common"? Andrewg scss 12:56, 29 June 2007 (CEST)

I have made quick edits to it, hopefully it is better. However, do note that in the original forum post as referenced in the external link, the digits Y and Z are mentioned. --unkx80 10:07, 30 June 2007 (CEST)

Thanks. I found http://www.sudoku.org.uk/cgi-bin/discus/show.cgi?tpc=29&post=4655 which seems to indicate ALS-XY-Wing and ALS-XZ are both specific instances of a more general "ALS-XY-Chain" strategy. I've been unable to implement ALS-XY-Wing (run out of time), but it appears it's important that the two restricted commons must be different, hence the different Y and Z mentioned originally. I'm really not sure. --Andrewg scss 08:40, 1 July 2007 (CEST)

Well, as far as I understand, Y and Z should be different, just like the XY-Wing. After all, the XY-Wing itself is a kind of ALS-XY-Wing: each bivalue call involved in the XY-Wing is itself an ALS. --unkx80 23:34, 1 July 2007 (CEST)

I was going to add the following, but as the page is locked I can't:

A possible Eureka notation for this elimination is:

(5=24791)ALS:r12c89,r3c8 - (1=2)r7c8 - (216=5)ALS:r7c46,r9c5 => r7c9 <> 5

Note, the reader must check the grid to ensure that r7c9 can see all the 5's in both ALS's and similarly for the links involving digits 1 and 2.

Using the ALS (245)r12c9 and a group node for (2)r12c8 we could also use ALS nodes in an AIC:

(5=42)ALS:r12c9 - (2)r12c8 = (2)r7c8 - (216=5)ALS:r7c46,r9c5 => r7c9 <> 5

which provides greater freedom for the locations of candidates in box 3

Dpbobelisk 13:22, 25 November 2007 (CET)

I added it in. Due to the large amount of spam, a number of pages have been locked from editing from anonymous users, but logged-in users should be able to edit. --unkx80 21:05, 27 November 2007 (CET)

Thanks Unkx80 - You formatted it better anyway! I'll try to remember next time Dpbobelisk 00:45, 28 November 2007 (CET)