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Jun 10 VH

 
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Lee



Joined: 10 Jun 2014
Posts: 24
Location: San Francisco
PostPosted: Tue Jun 10, 2014 1:02 pm    Post subject: Jun 10 VH Reply with quote
After basics

Code:

+-----------+--------+--------------+
| 7  13 6   | 8 5 2  | 4   9   13   |
| 5  38 4   | 1 7 9  | 68  2   368  |
| 2  9  18  | 6 4 3  | 178 5   178  |
+-----------+--------+--------------+
| 18 6  9   | 4 3 5  | 2   178 178  |
| 4  7  158 | 9 2 16 | 168 3   1568 |
| 3  15 2   | 7 8 16 | 9   4   156  |
+-----------+--------+--------------+
| 9  58 578 | 3 1 4  | 78  6   2    |
| 6  2  17  | 5 9 8  | 3   17  4    |
| 18 4  3   | 2 6 7  | 5   18  9    |
+-----------+--------+--------------+


w-wing on 18's in r3c3 and r4c1 eliminates 8 in r5c3 I think.
Then basics solves.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Tue Jun 10, 2014 1:48 pm    Post subject: Reply with quote
Welcome to the forum Les.

Quote:
w-wing on 18's in r3c3 and r4c1 eliminates 8 in r5c3 I think.


You don't have to think, you can be certain. I used the XY-Wing 15-8 pivoted in r5c2=>r9c1<>8.
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dongrave



Joined: 06 Mar 2014
Posts: 568
PostPosted: Wed Jun 11, 2014 12:26 pm    Post subject: Reply with quote
I missed Marty's XY wing but found the same XY wing with the pivot at r7c2. Weird. And then when I saw the 18's from those 2 XY wings, I noticed the UR of 18's (i.e. r4c1 & 8 and r9c1 & Cool that forces r4c8 to be 7 which also solves it.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Jun 11, 2014 2:46 pm    Post subject: Reply with quote
Don, that's common, to find the same XY-Wings in a puzzle. Technically, they're different even though they accomplish the same thing. Mine is 15-8, yours is 58-1.

The UR is known as a Type 1. If you're interested in URs, Keith wrote a well-known article here:

http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=3578
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Lee



Joined: 10 Jun 2014
Posts: 24
Location: San Francisco
PostPosted: Wed Jun 11, 2014 2:55 pm    Post subject: Reply with quote
Don

I think (there I go again) for the UR (unique rectangle) to actually work (maybe just a coincidence in this case) all the 4 corner squares must be in 2 rows, 2 columns, and 2 blocks. In this case they are in 4 blocks so the underlying conditions don't hold. Just pointing this out for general information. Maybe others would like a word on this. Thanks.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Jun 11, 2014 4:49 pm    Post subject: Reply with quote
Lee,

Absolutely right. I'm embarrassed that I didn't notice it. Embarassed
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dongrave



Joined: 06 Mar 2014
Posts: 568
PostPosted: Wed Jun 11, 2014 8:52 pm    Post subject: Reply with quote
What the heck? I knew that, how dumb of me! Sorry about that Marty, that's MY fault (ugh). Thanks for catching that Lee!
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lala



Joined: 15 Aug 2014
Posts: 6
Location: United States
PostPosted: Fri Aug 15, 2014 2:23 am    Post subject: Re: Jun 10 VH Reply with quote
I have been reading the boards and going through the archive trying out the different solving techniques. I managed to solve this one without looking at the board, but my solution was a bit different than those discussed and wanted to make sure my logic wasn't off:

Code:

+-----------+--------+--------------+
| 7  13 6   | 8 5 2  | 4   9   13   |
| 5  38 4   | 1 7 9  | 68  2   368  |
| 2  9  18  | 6 4 3  | 178 5   178  |
+-----------+--------+--------------+
| 18 6  9   | 4 3 5  | 2   178 178  |
| 4  7  158 | 9 2 16 | 168 3   1568 |
| 3  15 2   | 7 8 16 | 9   4   156  |
+-----------+--------+--------------+
| 9  58 578 | 3 1 4  | 78  6   2    |
| 6  2  17  | 5 9 8  | 3   17  4    |
| 18 4  3   | 2 6 7  | 5   18  9    |
+-----------+--------+--------------+


w-wing on 18's in r3c3 and r9c1 eliminates 1 in r8c3
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Fri Aug 15, 2014 3:33 pm    Post subject: Reply with quote
Your logic is perfect. There is also another W-Wing on 18; see opening comments in this thread.

Welcome to the forum. Feel free to post questions, solutions, comments, etc.
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