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Nov 27 VH

 
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hughwill



Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK

PostPosted: Fri Nov 27, 2015 12:33 pm    Post subject: Nov 27 VH Reply with quote

After basics:
Code:

+--------------+------------+----------+
| 13    7   4  | 5   13 6   | 2 8  9   |
| 238   289 5  | 78  37 789 | 1 6  4   |
| 6     89  18 | 4   2  189 | 3 5  7   |
+--------------+------------+----------+
| 5     14  9  | 2   8  134 | 6 7  13  |
| 12478 28  3  | 17  6  147 | 5 9  12  |
| 127   6   12 | 137 9  5   | 8 4  123 |
+--------------+------------+----------+
| 14    14  6  | 9   5  2   | 7 3  8   |
| 28    5   7  | 138 4  138 | 9 12 6   |
| 9     3   28 | 6   17 178 | 4 12 5   |
+--------------+------------+----------+

Play this puzzle online at the Daily Sudoku site
I managed this in 3:
Quote:
128 XY-Wing in boxes 1 and 4
followed by 781 XY-wing and 781 XYZ-wing
But I'm sure that there's a quicker way somewhere....

(Edit- Oh yes, I see. The X -wing on 8 in C14 replaces the two 781 wings...)

Hugh
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the_lock_man



Joined: 18 Dec 2012
Posts: 40
Location: Portsmarfff, UK

PostPosted: Fri Nov 27, 2015 12:58 pm    Post subject: Is it an X Wing? Reply with quote

I must admit to having a mental block about X Wings, but surely the possible 8 in R5C1 stops there being an X Wing on 8 in columns 1 & 4?

Apologies if I'm being a bit of a thicko.
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Marty R.



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

PostPosted: Fri Nov 27, 2015 4:14 pm    Post subject: Reply with quote

Lock man beat me to the punch. I was just about to write the same thing.
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Fri Nov 27, 2015 4:44 pm    Post subject: Reply with quote

It's easy to miss it - there are so many candidates in that cell that it practically runs into the next one! I think I saw an 8 X-Wing after the 1st XY-Wing (in two different columns) but I don't think it did much. Using only standard VH moves, I had to use the 3 wings that Hugh originally posted. Lately I'm on a one-step chain-finding kick too. Here's what I found (let me know if I screwed up again Marty). (3=1)r1c1-(1=8)r3c3-(8=2)r9c3-(2=8)r8c1-(8=13)r8c46-(1=7)r9c5-(7=3)r2c5=>r1c5=1; which solves it.

(Edit) I see now that I didn't need to use the 13 pair: (3=1)r1c1-(1=8)r3c3-(8=2)r9c3-(2=1)r9c8-(1=7)r9c5-(7=3)r2c5=>r1c5=1.
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Marty R.



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

PostPosted: Fri Nov 27, 2015 6:34 pm    Post subject: Reply with quote

Don, they're both fine. The only comment I want to make is about the conclusion =>r1c5=1. It's customary to show the conclusion as an elimination except under certain circumstances. In this case it would be => -3r1c5. After all, that's what pincers do, deny the existence of the pincer value.
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Fri Nov 27, 2015 7:06 pm    Post subject: Reply with quote

Marty R. wrote:
Don, they're both fine. The only comment I want to make is about the conclusion =>r1c5=1. It's customary to show the conclusion as an elimination except under certain circumstances. In this case it would be => -3r1c5. After all, that's what pincers do, deny the existence of the pincer value.

Oh! Of course. I see! Thanks Marty!
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hughwill



Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK

PostPosted: Sat Nov 28, 2015 9:25 am    Post subject: Re: Is it an X Wing? Reply with quote

the_lock_man wrote:
I must admit to having a mental block about X Wings, but surely the possible 8 in R5C1 stops there being an X Wing on 8 in columns 1 & 4?

Apologies if I'm being a bit of a thicko.



The X-wing on 8 appears after the 128 XY-Wing which sets r5c2 to 8 thus
removing the 8 in r5c1. Sorry, I should have made it clearer.

Hugh
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sat Nov 28, 2015 5:44 pm    Post subject: Reply with quote

I'm confused Hugh. I remembered seeing an 8 X-Wing yesterday after the 1st XY-Wing so I went back and looked today. I missed yours in C14 but I saw the one in R39 and they both appear to remove the same candidate (i.e. the 8 from r8c6). I'm pretty sure yesterday that I still had to perform the next XY-Wing (78-1 with pivot at r2c4) followed by a 13-8 XY-Wing (instead of the XYZ-Wing) with pivot at r8c6 so the X-Wing didn't do much for me (other than change the XYZ-Wing to an XY-Wing). Am I missing something?
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keith



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

PostPosted: Sat Nov 28, 2015 9:51 pm    Post subject: Reply with quote

After basics,
Code:
+-------------------+-------------------+-------------------+
| 13    7     4     | 5     13    6     | 2     8     9     |
| 238   289   5     | 78    37    789   | 1     6     4     |
| 6     89    18    | 4     2     189   | 3     5     7     |
+-------------------+-------------------+-------------------+
| 5     14    9     | 2     8     134   | 6     7     13    |
| 12478 28    3     | 17    6     147   | 5     9     12    |
| 127   6     12    | 137   9     5     | 8     4     123   |
+-------------------+-------------------+-------------------+
| 14    14    6     | 9     5     2     | 7     3     8     |
| 28    5     7     | 138   4     138   | 9     12    6     |
| 9     3     28    | 6     17    178   | 4     12    5     |
+-------------------+-------------------+-------------------+

There is an XY-wing 12-8 in C23.

Then, there is an X-wing (8) in R39. Yes, there is an XYZ-wing that makes the same elimination in R8C6. Or, there is an XY-wing -178 that takes out 1 in R45C6.

Keith
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sat Nov 28, 2015 10:37 pm    Post subject: Reply with quote

I'm still confused. Maybe I'm missing something. From Hugh's or Keith's grid I see a 12-8 XY-Wing with pivot at r6c3 that removes the 8 from r23c2. Then I perform basics until I get to the following grid:
Code:

 +--------------+------------+----------+
 | 13    7   4  | 5   13 6   | 2 8  9   |
 | 38    2   5  | 78  37 9   | 1 6  4   |
 | 6     9   18 | 4   2  18  | 3 5  7   |
 +--------------+------------+----------+
 | 5     14  9  | 2   8  134 | 6 7  13  |
 | 1247  8   3  | 17  6  147 | 5 9  12  |
 | 127   6   12 | 137 9  5   | 8 4  123 |
 +--------------+------------+----------+
 | 14    14  6  | 9   5  2   | 7 3  8   |
 | 28    5   7  | 138 4  138 | 9 12 6   |
 | 9     3   28 | 6   17 178 | 4 12 5   |
 +--------------+------------+----------+

And at this point I see Hugh's 8 X-Wing in C14 which removes the 8 from r8c6 and I see Keith's 8 X-Wing in R39 which removes the same candidate but after that I don't see a solution unless I play the 78-1 XY-Wing with pivot at r2c4 eliminating the 1 from r45c6 followed by a 13-8 XY-Wing with pivot at r8c6 removing the 8 from r2c4. But if that's the case, then the X-Wing didn't do much at all for me because it cost me an extra advanced move to make the last Wing an XY-Wing instead of an XYZ-Wing. Am I missing something?
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hughwill



Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK

PostPosted: Sun Nov 29, 2015 11:42 pm    Post subject: Reply with quote

dongrave wrote:
Am I missing something?


No, I don't think so.


Hugh Embarassed
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Mon Nov 30, 2015 12:07 am    Post subject: Reply with quote

hughwill wrote:
dongrave wrote:
Am I missing something?


No, I don't think so.

Hugh Embarassed

You have nothing to be embarrassed about Hugh! I make more mistakes than I do correct moves. It was just driving me crazy that I didn't see it! Keep up the great work!
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