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May 18 VH

 
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hughwill



Joined: 05 Apr 2010
Posts: 422
Location: Birmingham UK

PostPosted: Wed May 18, 2016 8:47 am    Post subject: May 18 VH Reply with quote

After basics:
Code:

+------------+------------+--------------+
| 4  12 1269 | 8  7   569 | 3    59  169 |
| 58 7  169  | 3  569 2   | 158  4   169 |
| 58 3  69   | 56 4   1   | 78   579 2   |
+------------+------------+--------------+
| 27 12 127  | 56 56  4   | 9    8   3   |
| 9  4  8    | 2  3   7   | 6    1   5   |
| 3  6  5    | 19 18  89  | 47   2   47  |
+------------+------------+--------------+
| 1  8  24   | 7  569 569 | 245  3   49  |
| 27 9  3    | 4  18  58  | 1257 6   17  |
| 6  5  47   | 19 2   3   | 147  79  8   |
+------------+------------+--------------+

Play this puzzle online at the Daily Sudoku site
This time a VH which is (by the rules) a true VH: Either
Quote:
79-4XY wing pivot r9c8 or 49-7 XY-Wing pivot r7c9
will solve this in one. (Select white area to view solution)
Hugh
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Marty R.



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

PostPosted: Wed May 18, 2016 10:57 pm    Post subject: Reply with quote

yep, beats a basics-only solution.
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dongrave



Joined: 06 Mar 2014
Posts: 563

PostPosted: Thu May 19, 2016 12:59 am    Post subject: Reply with quote

I had a couple more basic moves in Hugh's grid. The locked 5's in column 8 of box 3 removes it from r2c7 and then that gives you a hidden 25 pair in box 9. Then I found the 147 XYZ Wing with pivot at r9c7 (pincers at r9c3 and r8c9) so r9c8<>7 which solves it.
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Marty R.



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

PostPosted: Thu May 19, 2016 1:37 pm    Post subject: Reply with quote

dongrave wrote:
I had a couple more basic moves in Hugh's grid. The locked 5's in column 8 of box 3 removes it from r2c7 and then that gives you a hidden 25 pair in box 9. Then I found the 147 XYZ Wing with pivot at r9c7 (pincers at r9c3 and r8c9) so r9c8<>7 which solves it.


I don't understand. Why do locked 5s matter? The hidden pair on 25 (or as I prefer, a 1479 quad ) is already there. After finishing basics, there's no elimination from the XYZ-Wing that I can see.
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dongrave



Joined: 06 Mar 2014
Posts: 563

PostPosted: Thu May 19, 2016 3:23 pm    Post subject: Reply with quote

Marty R. wrote:
dongrave wrote:
I had a couple more basic moves in Hugh's grid. The locked 5's in column 8 of box 3 removes it from r2c7 and then that gives you a hidden 25 pair in box 9. Then I found the 147 XYZ Wing with pivot at r9c7 (pincers at r9c3 and r8c9) so r9c8<>7 which solves it.


I don't understand. Why do locked 5s matter? The hidden pair on 25 (or as I prefer, a 1479 quad ) is already there. After finishing basics, there's no elimination from the XYZ-Wing that I can see.

Hi Marty, It's not that the locked 5's matter; it's just another basic move that I saw. And after that, I saw that there was a hidden 25 pair so I pointed that out too. I think your point is that my phrasing of 'that gives you' is wrong though because the hidden pair is there already - but I didn't see it until I removed the 5 from r2c7. I posted what the XYZ wing does because I think it's easy to miss (Maybe you're not looking at the right XYZ Wing?) The 147 XYZ with pivot at r9c7 and pincers at r9c3 and r8c9 all have a 7 in them and they are all buddies with r9c8 so it can't be 7. Am I missing something?
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George Woods



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

PostPosted: Thu May 19, 2016 3:50 pm    Post subject: a different xy Reply with quote

nobody mentioned the 179 XY pivot r9c8
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Marty R.



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

PostPosted: Thu May 19, 2016 3:52 pm    Post subject: Reply with quote

Quote:
(Maybe you're not looking at the right XYZ Wing?)


That is correct. Embarassed Sad
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dongrave



Joined: 06 Mar 2014
Posts: 563

PostPosted: Thu May 19, 2016 3:57 pm    Post subject: Reply with quote

Marty R. wrote:
Quote:
(Maybe you're not looking at the right XYZ Wing?)


That is correct. Embarassed Sad

No big deal Marty! You're allowed to make mistakes! (It was't nearly as obvious as what I missed!) And I completely missed George's XY wing - and I looked for other wings for a while!
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