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Apr 6 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Mon Apr 05, 2010 11:36 pm    Post subject: Apr 6 VH Reply with quote

Two steps.
After the W-Wing 47 in r38c46 which eliminates 4 in r3c6 we have
Code:

+--------+------------+-----------+
| 9 2  7 | 1  6  8    | 3  5  4   |
| 8 6  4 | 35 2  35   | 1  7  9   |
| 1 3  5 | 4  79 79   | 8  6  2   |
+--------+------------+-----------+
| 5 18 3 | 67 4  17   | 9  2  68  |
| 7 18 2 | 36 19 139  | 46 48 5   |
| 6 4  9 | 25 8  25   | 7  1  3   |
+--------+------------+-----------+
| 3 9  6 | 28 17 1247 | 5  48 78  |
| 2 5  1 | 78 3  47   | 46 9  678 |
| 4 7  8 | 9  5  6    | 2  3  1   |
+--------+------------+-----------+

An XY-Wing (78) (76)pivot in r4c4 (68) eliminating 8 in r8c9 solving the puzzle.
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Tue Apr 06, 2010 11:03 am    Post subject: Reply with quote

I went chain hunting and this one does it in one...

Quote:
(7=4)r8c6-(4=6)r8c7-(6=4)r5c7-(4=8)r5c8-(8=1)r5c2-(1=8)r4c2-(8=6)r4c9-(6=7)r4c4; r78c4<>7, r4c6<>7
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Tue Apr 06, 2010 12:04 pm    Post subject: 3 xy wings! Reply with quote

for me it was 3 XY wings though whether it was neccesary it was certainly sufficient:-

First a 179 allowed a 479 to put a 1 in r7c5 and after a few more entries a 479 finished the job by putting a 2 in r7c4!
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Tue Apr 06, 2010 12:49 pm    Post subject: Reply with quote

Two Type 6 URs (47) (78). 179 xy wing. BUG+1
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Tue Apr 06, 2010 3:32 pm    Post subject: Reply with quote

Obviously a different kind on VH. I played two W-Wings and got two eliminations from the same Hidden UR (78).
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Tue Apr 06, 2010 3:52 pm    Post subject: Reply with quote

So far as I can see, four XY-wings are required: 1-79, 4-79, 67-8, 6-78.

(Recall, you should be able to solve it with only X, XY, and XYZ wings.)

Keith
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Tue Apr 06, 2010 4:14 pm    Post subject: Reply with quote

Keith, interesting comment - I am new to this site and was wondering what sort of level VH is meant to be.

There seems to be a strong bias in the setter to xy-wings - which are almost always necessary it seems. Avoiding them is an interesting challenge!

I cut my teeth on the mepham diabolicals which are harder (or used to be) and colouring is usually the best 'bang for buck' weapon in the armoury.

Enjoying dannys puzzles too..
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Wed Apr 07, 2010 5:48 am    Post subject: Reply with quote

I really do resemble that remark Peter.
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Wendy W



Joined: 04 Feb 2008
Posts: 144

PostPosted: Thu Apr 08, 2010 12:04 am    Post subject: Reply with quote

I dunno, guys -- I did it with only two xy-wings: 678 and then 179. Took me a while to find them, though!
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RobertRattley



Joined: 24 Jun 2007
Posts: 118
Location: Australia

PostPosted: Sun Apr 25, 2010 7:40 am    Post subject: Reply with quote

I concur with Keith. I've solved all Daily Sudoku puzzles, and advanced techniques beyond those 3 kinds of wings have never been needed (pleasurable though different techniques may be to other solvers).

Four xy wings! Most unusual.

I do note Wendy's comments, but I don't feel in the mood to revisit the puzzle. Yes, if you're right Wendy, it takes a while to find them! Even though basics seem to go so far.

This is a beautifully constructed puzzle. Congratulations to the designer.
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