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Marty R. · Posted: Sun May 21, 2006 5:48 am Post subject: Finned X-Wing

I thought I read somewhere that there can be two fins, not just one. Is that correct? I hope I've provided enough information by showing only the "6s" in the relevant boxes. Note that there would be an X-Wing in r18 and c18 except for the two fins in r1c7 and r1c9. If there was just the one fin, I could conclude that the "6s" in r2c8 and r3c8 must go, but with the two fins, to make the same conclusion, I'd have to conclude that there must be a "6" in r1 of box 3. If that is actually the case, I don't know how to reason that out.

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

keith · Posted: Sun May 21, 2006 2:57 pm Post subject: Fork

Marty,

Note there is a "fork" in R2 and R3 which eliminates the <6> in R1C1.

Also, you can use coloring to connect R8C8 and R2C3, to eliminate <6> in R2C8.

Keith

Marty R. · Posted: Sun May 21, 2006 4:47 pm Post subject:

"I hope I've provided enough information by showing only the "6s" in the relevant boxes. "

Apparently, I misled. I only showed the "6s" in the boxes where the potential Finned Wing was. There are a few other "6s" floating around, particularly in r3c4. I believe this would preclude both David's X-Wing and Keith's coloring.

I don't know what a "fork" is.

So my lazy little shortcut backfired. I'm sorry. :oops:

P.S. It's now 15 minutes since I posted the above. I should have searched first. David answered my question on May 4.

keith · Posted: Sun May 21, 2006 5:17 pm Post subject: "Fork"

Marty,

I think you probably know what a "fork" is, but by another name. I posted an explanation in the Saturday puzzle thread:

http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=861

Tracy calls it multi-coloring, Havard (in his article on Strong Links) calls it a skyscraper.

Keith

Marty R. · Posted: Sun May 21, 2006 9:28 pm Post subject: Re: "Fork"

ravel · Joined: 21 Apr 2006 Posts: 536

Since i also had mixed the names sometimes:

Strong links are equivalent to advanced coloring.

Multicoloring is a superset (allowing more eliminations), but it is a bit complicated with it to make the eliminations of 3 or more strong links. E.g. for 3 strong links A-a,B-b,C-c i would argue about that:
a and B share a unit => A or b have to be the number x.
b and C share a unit => B or c have to be x.
Since b and B share a unit, also A or c have to be x.

Marty R. · Posted: Mon May 22, 2006 3:47 pm Post subject:

Multi-coloring is something I'm going to have to live without, at least for awhile, because I just can't get it to penetrate my thick skull.