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Sept 19 VH

 
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roaa



Joined: 18 Apr 2009
Posts: 71
Location: Sweden

PostPosted: Thu Sep 19, 2013 8:09 am    Post subject: Sept 19 VH Reply with quote

One step solution: xy-wing (245), pivot r7c1, forces r4c7=6, which makes it.
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hughwill



Joined: 05 Apr 2010
Posts: 165
Location: Birmingham UK

PostPosted: Thu Sep 19, 2013 8:54 am    Post subject: Sept 19 VH Reply with quote

After basics:
Code:

+------------+---------+------------+
| 8  1   4   | 6  7 25 | 3  9   25  |
| 2  5   6   | 9  3 1  | 4  8   7   |
| 7  9   3   | 8  4 25 | 1  256 256 |
+------------+---------+------------+
| 9  23  125 | 4  6 7  | 8  25  13  |
| 6  8   12  | 12 5 3  | 7  4   9   |
| 45 234 7   | 12 8 9  | 26 256 13  |
+------------+---------+------------+
| 45 247 8   | 57 1 6  | 9  3   24  |
| 3  267 25  | 57 9 4  | 26 1   8   |
| 1  46  9   | 3  2 8  | 5  7   46  |
+------------+---------+------------+

Play this puzzle online at the Daily Sudoku site

Roaa said:

Quote:
One step solution: xy-wing (245), pivot r7c1, forces r4c7=6, which makes it.


Yes, I got that too, but only after going up the 123 XY blind alley and
before seeing the (boring?) one-step Type 1 UR on 25 in boxes 2 and 3.
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roaa



Joined: 18 Apr 2009
Posts: 71
Location: Sweden

PostPosted: Thu Sep 19, 2013 1:27 pm    Post subject: Reply with quote

I also saw both these before I landed in the best(?) xy 245 solution.
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Dart45



Joined: 16 Apr 2008
Posts: 14
Location: Canada

PostPosted: Thu Sep 19, 2013 6:10 pm    Post subject: Reply with quote

Huh? What? r4c7 is not 6! So what's up here?
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Thu Sep 19, 2013 8:04 pm    Post subject: Reply with quote

Dart45 wrote:
Huh? What? r4c7 is not 6! So what's up here?


Maybe a typo. R8c7 is 6 after the 2 is eliminated.
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RobertRattley



Joined: 24 Jun 2007
Posts: 53
Location: Australia

PostPosted: Mon Sep 23, 2013 2:18 pm    Post subject: Reply with quote

I like 'very hard' puzzles that need a 'hard' step or two on the way. Here I needed a pair 46 in row 9.

Like roaa I also saw the two independent xy wings. I was curious as to whether they were both needed. I confirmed that the 123 xy wing was not enough (hughwill's "blind alley") and not even necessary: the 245 xy wing was necessary and sufficient.
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