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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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 Posted: Thu Jun 12, 2008 12:29 am Post subject: Jun 12 |
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| XY-Wing 36-35-56 eliminae 6 from R2C6. This reveals another XY-Wing 39-69-36 which eliminates 3 from R5C6, which solves the puzzle. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Jun 12, 2008 3:52 am Post subject: |
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| I used a W-Wing, two multi-colorings on 3, then an XY-Wing on 69-36-39 with pincer coloring finished it off. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Jun 12, 2008 12:19 pm Post subject: |
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For me, a finned x-wing which eliminated 6 from r5c4 did the job. 
Ted |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Thu Jun 12, 2008 5:38 pm Post subject: VH |
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Skyscraper in <6>.
Earl |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Thu Jun 12, 2008 6:16 pm Post subject: |
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| Same skyscraper on <6>. Though earlier I used an x-wing on <3> in R17 which probably wasn't necessary. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Thu Jun 12, 2008 11:15 pm Post subject: |
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| Quote: | | For me, a finned x-wing which eliminated 6 from r5c4 did the job. |
Sorry - just noticed. What is a finned x-wing? |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Jun 13, 2008 1:26 am Post subject: |
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| cgordon wrote: | | Quote: | | For me, a finned x-wing which eliminated 6 from r5c4 did the job. |
Sorry - just noticed. What is a finned x-wing? |
Craig, the reference I used is http://www.sudocue.net/guide.php. Hope this helps.
Ted |
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Dougs
Joined: 24 Apr 2008
Posts: 2
Location: London. UK
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| Posted: Sat Jun 14, 2008 4:38 pm Post subject: |
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| Sorry - just catching up. Can someone show me where the skyscrapper is please? |
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Steve R
Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England
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| Posted: Sat Jun 14, 2008 6:27 pm Post subject: |
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This is where the going gets a little harder:
| Code: | +-----------------------------------------------+
| 69 *369 1 | 5 *369 8 | 7 4 2 |
| 2 4 369 | 1 7 369 | 5 368 68 |
| 7 8 5 | 4 36 2 | 1 36 9 |
-------------------------------------------------
| 5 2 69 | 8 1 7 | 3 69 4 |
| 8 69 4 | 36 3569 3569 | 2 7 1 |
| 3 1 7 | 2 4 69 | 89 5 68 |
-------------------------------------------------
| 1 *35 8 | 9 *35 4 | 6 2 7 |
| 69 569 2 | 7 8 56 | 4 1 3 |
| 4 7 36 | 36 2 1 | 89 89 5 |
+-----------------------------------------------+ |
There is an X-Wing for 3 based on rows 1 and 7 so 3 may be eliminated from r35c5, which brings us to:
| Code: | +-------------------------------------------+
| 69 369 1 | 5 39 8 | 7 4 2 |
| 2 4 39 | 1 7 39 | 5 68 68 |
| 7 8 5 | 4 6 2 | 1 3 9 |
---------------------------------------------
| 5 2 *69 | 8 1 7 | 3 69 4 |
| 8 69 4 | *36 59 3569 | 2 7 1 |
| 3 1 7 | 2 4 69 | 89 5 68 |
---------------------------------------------
| 1 35 8 | 9 35 4 | 6 2 7 |
| 69 569 2 | 7 8 56 | 4 1 3 |
| 4 7 *36 | *36 2 1 | 89 89 5 |
+-------------------------------------------+ |
The finned X-Wing (skyscraper) for 6 based on columns 3 and 4 eliminates 6 from r5c2 and gets you home.
Steve |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Jun 14, 2008 8:48 pm Post subject: |
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| Quote: | | The finned X-Wing (skyscraper) |
Steve: In a post above I stated I had used a Skyscraper. Then your subsequent post said you used a Finned X-Wing. I asked what one of these was - and you directed me to a Sudoku reference. Having read it -and your latest post, I'm not convinced a finned X-Wing and a Skyscraper are the same animal. Your solution is identical to my Skyscraper -it's unsymmetrical and only has 2 candidates per column. |
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Steve R
Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England
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| Posted: Sat Jun 14, 2008 10:07 pm Post subject: |
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Craig
I think you’re mixing me up with Ted. If I have ever directed you to a site which you found confusing, I apologise for it.
Personally I cannot distinguish between “skyscraper” and “finned X-Wing.” You may, if you choose. The only point I would make is that, if it actually makes a difference to your meaning, you would do well to explain the structure you have in mind since others may draw a distinction in a different way.
Steve |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Jun 14, 2008 11:28 pm Post subject: |
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| Steve: Awfully sorry. It was Ted's fault. I'll examine the situation - though hopefully someone with more acumen than what I got - will determine whether a Finned X -wing is a Skyscraper. Perhaps it's all just semantics. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Jun 14, 2008 11:55 pm Post subject: |
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| cgordon wrote: | | Steve: Awfully sorry. It was Ted's fault. I'll examine the situation - though hopefully someone with more acumen than what I got - will determine whether a Finned X -wing is a Skyscraper. Perhaps it's all just semantics. |
Nobody's ever accused me of having acumen, but I can't understand this confusion. A Finned X-Wing is an "almost X-Wing", where there is an extra candidate or two to preclude a real X-Wing. A Skyscraper is strong links in two parallel rows or columns where one candidate from each pair of strong links is in the same row/column.
As far as I know, the understanding of these terms is pretty much the same by most people. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sun Jun 15, 2008 12:21 am Post subject: |
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| I've lived with Skyscrapers for a long time. I do not like the idea of Finned X Wings moving in and calling theselves Skyscrapers. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sun Jun 15, 2008 11:38 am Post subject: |
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In Steve R's first grid there is a W-wing <36> that solves the puzzle in one step by taking out <3> in R9C4.
Keith |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Mon Jun 16, 2008 2:10 am Post subject: |
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Perhaps it will help settle the nomenclature confusion to point out that a Skyscraper can be viewed (not really that helpfully in my opinion) as two overlapping Sashimi X-Wings. And, Sashimi Fish are Finned Fish where the piece of the fish that shares a box with the Fin is missing.
Here is a simplified diagram of two Finned X-Wings and the corresponding Sashimi X-Wings:
| Code: | Finned X-Wings:
+-------+-------+-------+ +-------+-------+-------+
| . . . | . . . | . . . | | . . . | . . . | . . . |
| ~ X ~ | ~ ~ X | ~ ~ ~ | | ~ X ~ | ~ ~ X | ~ ~ ~ |
| . . . | . . . | . . . | | . . . | . . . | . . . |
+-------+-------+-------+ +-------+-------+-------+
| . . . | . . v | . . . | | . . . | . . v | . . . |
| ~ X ~ | X X X | ~ ~ ~ | | ~ X ~ | X ~ X | ~ ~ ~ |
| . . . | . . v | . . . | | . . . | . . v | . . . |
+-------+-------+-------+ +-------+-------+-------+
2-cell Fin 1-cell Fin
Sashimi X-Wings:
+-------+-------+-------+ +-------+-------+-------+
| . . . | . . . | . . . | | . . . | . . . | . . . |
| ~ X ~ | ~ ~ X | ~ ~ ~ | | ~ X ~ | ~ ~ X | ~ ~ ~ |
| . . . | . . . | . . . | | . . . | . . . | . . . |
+-------+-------+-------+ +-------+-------+-------+
| . . . | . . v | . . . | | . . . | . . v | . . . |
| ~ X ~ | X X ~ | ~ ~ ~ | | ~ X ~ | X ~ ~ | ~ ~ ~ |
| . . . | . . v | . . . | | . . . | . . v | . . . |
+-------+-------+-------+ +-------+-------+-------+
2-cell Fin 1-cell Fin |
"~" means "not X" and "v" denotes the victim cells.
Note that the Sashimi X-Wing with a 1-cell Fin is really just "half of a Skyscraper." (If you see it alternately as a Sashimi X-Wing that has its Fin in the top row, then the other two Skyscraper victims are revealed.)
Most people only use the Sashimi X-Wing name to refer to the 2-cell Fin case. And, some people don't use the term "Sashimi" at all and refer to all varieties of such creatures as Finned Fish. This problem of the "vanishing fish" only occurs with Sashimi X-Wings; it does not occur with Sashimi Swordfish or Sashimi Jellyfish. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Jun 16, 2008 7:54 pm Post subject: |
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Asellus: Correct me if I'm wrong but aren't all of your examples also ERs where the bottom left X is also a victim?
Cheers, Craig
PS. I like your use of diagrams with tildes ~ denoting "not X' and "v" for victims. I have an old but similar diagram for Type 2 (?) W-wings except there are no "v"s and I can't figure out whether the tildes mean "aren't" or "can't be". |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Mon Jun 16, 2008 9:42 pm Post subject: |
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| cgordon wrote: | | Asellus: Correct me if I'm wrong but aren't all of your examples also ERs where the bottom left X is also a victim? |
They would be if all the cells with dots did not contain X. But, the cells with dots can be anything, which I should have mentioned. So, for instance...
| Code: | +-------+-------+-------+
| . . . | . . . | . . . |
| ~ X ~ | ~ ~ X | ~ ~ ~ |
| . . . | . . . | . . . |
+-------+-------+-------+
| . . . | . X v | . . . |
| ~ X ~ | X ~ X | ~ ~ ~ |
| . . . | X . v | . . . |
+-------+-------+-------+ |
is still a Finned X-Wing. But, it is not an ER.
By the way, I have so far always been able to find another method that accomplishes the same thing in the case of an ER. So it isn't surprising that an ER might also form a Finned Fish of some sort.
Regarding tildes, they are used for "not" in some math symbol conventions, so it's a natural choice. Plus, others have used them before me here so I'm just following suit. I agree that the tilde should not be used to denote victims. For that, "v" or "-X" is clearer. |
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RobertRattley
Joined: 24 Jun 2007
Posts: 118
Location: Australia
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| Posted: Sat Jun 21, 2008 6:09 pm Post subject: |
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I've been able to solve EVERY "very hard" using only basics, x-wing or swordfish, and xy and xyz wings. It seems to me that "very hard"s are designed to need only these techniques.
This time I didn't spot prakash's elegant pair of x wings. I found a swordfish 9, creating a fulcrum 356 for an xyz wing. |
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