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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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 Posted: Sun Apr 25, 2010 10:49 pm Post subject: April 26 VH |
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Surprised to see no posts on this, but any way, an X Wing on 8 and an xyz wing on 489 did the trick.
(Edited by Marty to correct date in subject line).
Sorry for the goof up with the date. This was in response to the VH from April 24 and not 26. Who would have known that April 26th would also have been a VH
Last edited by prakash on Tue Apr 27, 2010 2:08 am; edited 3 times in total |
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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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| Posted: Mon Apr 26, 2010 12:05 am Post subject: April 26 VH |
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Two steps
1. UR 39 removes 39 in r7c1 followed by
2. XY-Wing 59 57 79 eliminating 9 in r7c2 and r9c6 solves the puzzle. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Apr 26, 2010 12:38 am Post subject: |
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| I couldn't find an X-Wing on 8. An XY-Wing (395) pivoted in r7c2 will do it, as will a chain. I can't notate it, but r8c5=1 proves r7c4=5, making r7c5<>5. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Apr 26, 2010 12:30 pm Post subject: |
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| There are two UR's available 39 and a Type 4 on 79. Still needed an xy wing on 579. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Apr 26, 2010 2:34 pm Post subject: |
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This puzzle also has an "almost" one step solution.
| Code: | *-----------------------------------------------------------*
| 39 39 5 | 28 7 6 | 4 1 28 |
| 6 4 2 | 58 159 #189 | 3 7 #89 |
| 8 1 7 | 23 4 39 | 6 5 29 |
|-------------------+-------------------+-------------------|
| 2 8 6 | 7 3 5 | 9 4 1 |
| 4 5 9 | 1 6 2 | 7 8 3 |
| 1 7 3 | 9 8 4 | 5 2 6 |
|-------------------+-------------------+-------------------|
| 3579 39 1 | 358 59 3789 | 2 6 4 |
| 35 2 4 | 6 15 13 | 8 9 7 |
| 79 6 8 | 4 2 79 | 1 3 5 |
*-----------------------------------------------------------* |
We "almost" have a 89 pair in r2c69, marked #; however we have the additional digit 1 in r2c6. This provide a strong inference that either r2c69=89 or r2c6=1; one of these two conditions must be true. So, looking at both conditions we find:
If r2c69=89, then r2c4<>8 & r2c5<>9,
If r2c6=1, then r8c6=3, then r3c6=9; r2c5<>9.
Thus for either condition, r2c5<>9 to complete the puzzle.
The (189) configuration in r2c69 is an ALS, which provides multiple strong inferences between the its components. We could write a simple AIC based on this ALS: ALS189[(9)r269 = (1)r2c6]r2c69 - (1=3)r8c6 - (3=9)r3c6; r2c5<>9.
I hope this explanation may help others gain insight into another tool for their bag of tricks.
Ted |
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dulaby
Joined: 02 May 2007
Posts: 13
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| Posted: Mon Apr 26, 2010 4:39 pm Post subject: |
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| XY-WING(35.39,59) ON BOXES 7 AND 8 IS ENOUGH |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Mon Apr 26, 2010 5:23 pm Post subject: |
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I used the XY-wing 3-59. It solves R8C5 as 1.
Keith |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Apr 26, 2010 5:27 pm Post subject: |
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| tlanglet wrote: | This puzzle also has an "almost" one step solution.
...
I hope this explanation may help others gain insight into another tool for their bag of tricks.
Ted |
Ted, old friend and brother in arms,
please tell me that you're not serious.
You're not really going to throw an "almost" whatever mumbo jumbo fillet de fish in sue de coq, marinated in sashimi wasabi at this puzzle that needs nothing more than a simple xy-wing to solve?
This "ok there are only 2 possibilities, let's assume that x is ... then ... becomes ... and further on ... and then ...but on the other hand if x were ... then " OMG  I did that before I heard of things like x-wing or xy-wing, let alone those other beauties we've become familiar with.
Why, oh why ... return to the dark days when forcing nets were the only tool available? BTW you could call cell r1c1 (or any other unsolved cell for that matter) an "almost" single and work from there...
Going to create an "almost empty" glass of good Beaujolais now and drink to all puzzles that can be solved with "almost" super-duper-excessive methods
Cheers,
Nataraj |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Apr 26, 2010 10:06 pm Post subject: |
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No, Nataraj ole' buddy, it is not my intent to offer an onslaught of "almost' solutions for puzzles on this special thread. The thread where I was fustrated when posts did not provide sufficient info to help me to learn new steps such as xy-wings, xyz-wings, etc. The thread where I spent many, many hours learning the rules of Sudoku by posting questions which were quickjy answered by many including yourself.
I only hoped to crack open the door to more of the Sudoku world for those interested folks who may one day pursue a puzzle that does not contain a xy-wing and then wonder "what now"?
Did someone say that "Variety is almost the spice of life"?
Ted  |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Tue Apr 27, 2010 2:15 pm Post subject: |
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| I must say that the almost school has been very useful to me in the advanced puzzles and has made me think differently about puzzles. |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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| Posted: Tue Apr 27, 2010 4:41 pm Post subject: |
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| Nataraj wrote: | | Going to create an "almost empty" glass of good Beaujolais now |
That cracked me up and made me jealous at the same time  .
A fine player named Udosuk once tried to define sudoku elegance. To paraphrase, he said that an elegant solution uses the simplest methods to cause the greatest amount of damage in the fewest number of moves.
Others prefer metaphors decrying the use of steam rollers or sledge hammers to squash a bug...
Still, there are mitigating circumstances when it comes to elegance.
* One may be trying to make a point.
* It can be more fun to use alternatives to the same-ole-same-ole.
* It’s good to keep in practice on different techniques so that when they’re actually needed they can be remembered and applied.
* Some can see the more obscure approach before the simple one. I think we all have techniques we can spot at a glance and others we’re cloudy on even when pointed out.
Usually when I use a double-barreled shotgun on a mosquito I preface it with a disclaimer like, “This isn’t necessary but it’s what I saw...” |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Apr 27, 2010 7:37 pm Post subject: |
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Ted, Luke, Mogulmeister,
to be sure, I do appreciate the potential of an "almost" approach, be it all sorts of finned fishy creatures, or almost locked sets. If it were possible to carry that approach over to a more pattern based method, less inference chain/forcing net style, then ... wow what a formidable weapon in our armory that would be. In the case of finned fish, the "victim" and the "fin" are usually in close proximity, which makes it very easy to see the connection ...
About "almost" patterns in general ...
At this time, I feel rather ambivalent, not sure if we're about to "cyborg" ourselves: the advantage of catching a few more "criminals" (i.e. difficult puzzles) bought at the steep price of replacing large parts of our natural body (or mind) by advanced circuitry and hardened steel?
Those questions being far too complex for me, I return to my "almost" empty glass (right you are, Luke, in envying me ) of Beaujolais, Fleurie 2007, to be exact ... mmmhhhh
Nataraj |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Wed Apr 28, 2010 2:03 am Post subject: |
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| Nataraj wrote: |
Usually when I use a double-barreled shotgun on a mosquito I preface it with a disclaimer like, “This isn’t necessary but it’s what I saw...” |
Nat, imho the only glass of "good" Beaujolais is a dead one!  |
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