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Apr 12 VH

 
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 941
Location: Rimini, Italy
PostPosted: Tue Apr 12, 2022 9:11 am    Post subject: Apr 12 VH Reply with quote
Hi everyone,

Code:

+------------+-----------+-----------+
| 3 2679 5   | 1   4 279 | 67 8  26  |
| 8 4    267 | 23  5 27  | 9  1  236 |
| 1 279  27  | 239 6 8   | 37 5  4   |
+------------+-----------+-----------+
| 4 8    9   | 26  3 1   | 5  26 7   |
| 7 5    23  | 269 8 29  | 36 4  1   |
| 6 23   1   | 4   7 5   | 8  23 9   |
+------------+-----------+-----------+
| 5 1    8   | 7   2 36  | 4  9  36  |
| 9 36   4   | 8   1 36  | 2  7  5   |
| 2 367  367 | 5   9 4   | 1  36 8   |
+------------+-----------+-----------+

Play this puzzle online at the Daily Sudoku site

Quote:
XY-Wing 2,3,7 in r3c37,r5c3 and -3 in r5c7
or
Skyscraper with number 3 in r59c3,r69c8 and -3 in r5c7,r6c2
or
2 String Kite with number 3 in r5c37,r69c8 and -3 in r9c3
2 String Kite with number 3 in r59c3,r6c28 and -3 in r9c8
or
W-Wing 3,6 in r8c2,r9c8 SL with number 3 in r6c28 and -6 in r9c23
W-Wing 3,6 in r5c7,r9c8 SL with number 3 in r59c3 and -6 in r4c8


Ciao Gianni
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TomC



Joined: 30 Oct 2020
Posts: 358
Location: Wales
PostPosted: Tue Apr 12, 2022 9:30 am    Post subject: Reply with quote
Code:

+-------------+-----------+-------------+
| 3 2679 5    | 1   4 279 | 67d  8  26  |
| 8 4    267  | 23  5 27  | 9    1  236 |
| 1 279  27a  | 239 6 8   | 37x  5  4   |
+-------------+-----------+-------------+
| 4 8    9    | 26  3 1   | 5    26 7   |
| 7 5    23b  | 269 8 29  | 36c  4  1   |
| 6 23   1    | 4   7 5   | 8    23 9   |
+-------------+-----------+-------------+
| 5 1    8    | 7   2 36  | 4    9  36  |
| 9 36   4    | 8   1 36  | 2    7  5   |
| 2 367  367  | 5   9 4   | 1    36 8   |
+-------------+-----------+-------------+

XY chain a-d or d-a gives pincers on <7> in <a> and <d> means x is not <7>
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Mogulmeister



Joined: 03 May 2007
Posts: 1151
PostPosted: Tue Apr 12, 2022 1:45 pm    Post subject: Reply with quote
Just another way of looking at a puzzle a bit differently. This technique is not a designated VH but can be useful when looking at sudokus at all levels.

Looking at Tom's grid:

Look at r3c23 and you see an almost locked pair (ANP) - both cells contain 2 and 7. However there's a 9 in r3c2 stopping a naked pair.

So, only two possibilities exist: either the naked pair <27> is true or the 9 in r3c2 is true.

If the NP is true then the <27> pair eliminate the 7 in x solving the puzzle.

If the NP is false then the <9> in r3c2 removes the 9 in r3c4 making r5c4 = 9. This makes r5c6 = 2. At this point we join Tom's loop at b = 3 and follow it out where once again the 7 in x is eliminated solving the puzzle.

Conclusion is that whether the naked pair is true or not - the answer is x can not be 7.
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