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Vanhegan Fiendish September 10

 
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Fri Sep 11, 2009 1:54 pm    Post subject: Vanhegan Fiendish September 10 Reply with quote
I completed this puzzle in two steps, but the first move was the hard one for me.

Code:

+-------+-------+-------+
| 4 8 . | 2 . . | . 7 3 |
| 6 . 5 | . 3 . | 4 . 8 |
| . 3 7 | 8 . . | 6 1 . |
+-------+-------+-------+
| . . . | . . . | 2 . 7 |
| . 5 . | . . . | . 6 . |
| 9 . 4 | . . . | . . . |
+-------+-------+-------+
| . 1 6 | . . 3 | 7 9 . |
| 7 . 3 | . 8 . | 1 . 6 |
| 5 2 . | . . 7 | . 8 4 |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

My two steps:
Quote:
extended xy-wing 35-9 with vertex 35 in r4c4 and pincer 59 in r4c6. The extended pincer is: (3)r4c4 - (3=4)r5c4 - (4=8)r5c6 - (8=9)r5c7 - (9)r5c9 = (9)r3c9. Thus, r3c6<>9
This opened up a xy-wing 45-9 with vertex 45 in r3c6 and pincer 59 in r3c9. The extended pincer is: (4)r3c6 - (4=8)r5c6 - (8=9)r5c7. Thus, r5c9<>9.


I suspect a one step solution is available but ...............

Ted
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sat Sep 12, 2009 4:47 am    Post subject: Reply with quote
Ted, nice work on the extended xy-wings.
for a one stepper, one way would be to perform some major medusa on this grid of mostly bi-values.
hint, start with the {5,9} pair in box 3.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Sep 12, 2009 4:21 pm    Post subject: Reply with quote
Ted,

I've seen the term "Extended XY-Wing" used to describe a few different things, thus making the term confusing.

However, this is the first time I've seen reference to an XY-Wing that involves only two cells. Have I been living in a cave? On the other hand, if this type of wing is new and/or not widely known, perhaps you could explain it in the Solving Techniques sub-forum.

Thanks.
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Sat Sep 12, 2009 8:36 pm    Post subject: Reply with quote
Marty R. wrote:
Ted,

I've seen the term "Extended XY-Wing" used to describe a few different things, thus making the term confusing.

However, this is the first time I've seen reference to an XY-Wing that involves only two cells. Have I been living in a cave? On the other hand, if this type of wing is new and/or not widely known, perhaps you could explain it in the Solving Techniques sub-forum.

Thanks.


Not sure what you are thinking of Marty.
I see a 4 cell xy-chain, or an extended xy-wing.

In fact at least two, with different eliminations.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Sun Sep 13, 2009 10:50 pm    Post subject: Reply with quote
Marty R. wrote:
Ted,

I've seen the term "Extended XY-Wing" used to describe a few different things, thus making the term confusing.

However, this is the first time I've seen reference to an XY-Wing that involves only two cells. Have I been living in a cave? On the other hand, if this type of wing is new and/or not widely known, perhaps you could explain it in the Solving Techniques sub-forum.

Thanks.

Marty,

I am sorry about any confusion I may have caused by the wording/terminology I used in this post. Terminology seems to be a re-occurring problem when posting on this forum. Recently, I used the term "xy-wing with pseudocell pincer", which resulted in questions/confusion by some. I also recall a furry of posts about terminology several months ago that lead to a suggestion that we, the folks that participate on this website, formulate a set of common definitions in order to reduce the confusion factor, but the effort never materialized. Lately, I have been posting less frequently simply because the effort to prepare a "good" post that explains what steps I used without writing a full novel but provides adequate detail exceeds the pleasure of sharing with others.

In this post, I had two xy-wings; both had vertex, XY, and one pincer, say XZ, in a common row/column/box. The second pincer, YZ, was found by following the logical implications of setting the vertex to Y and looking for Z. This "implication" process is an AIC, and I used that notation to post the steps I used. The overall end result of this process is an AIC, and maybe I should simply call it that. However, I always start the process looking for a xy-wing and so that is what I have named it in my posts.

So no, I have not found a wonderful, new technique but am only struggling to post a step that does not have a fixed, unique pattern and thus does not have a fixed name.

Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Mon Sep 14, 2009 12:53 am    Post subject: Reply with quote
Ted, I appreciate the explanation. AICs are not in my arsenal, unfortunately. I do hope you can find a way to up the frequency of your posts to its previous level.
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