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Sep 17 VH

 
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 641
Location: Rimini, Italy

PostPosted: Fri Sep 17, 2021 8:12 am    Post subject: Sep 17 VH Reply with quote

Hi everyone

Code:

+----------------+--------------+------------+
| 23689 269  389 | 4  7    25   | 18 158 19  |
| 4     29   89  | 1  25   3    | 6  578 79  |
| 1     7    5   | 9  6    8    | 3  4   2   |
+----------------+--------------+------------+
| 289   1    489 | 5  234  24   | 7  68  36  |
| 5     3    6   | 78 19   79   | 18 2   4   |
| 28    24   7   | 38 1234 6    | 5  9   13  |
+----------------+--------------+------------+
| 7     8    2   | 6  49   1    | 49 3   5   |
| 369   4569 1   | 2  3459 4579 | 49 67  8   |
| 369   4569 349 | 37 8    4579 | 2  167 167 |
+----------------+--------------+------------+

Play this puzzle online at the Daily Sudoku site

XY-Wing 1,3,8 in r5c7,r6c49 and -8 in r5c4

Ciao Gianni
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TomC



Joined: 30 Oct 2020
Posts: 144
Location: Wales

PostPosted: Sat Sep 18, 2021 6:08 am    Post subject: Reply with quote

Code:

+------------------+----------------+------------+
| 23689  269   389 | 4   7     25   | 18 158 19  |
| 4      29    89  | 1   25    3    | 6  578 79  |
| 1      7     5   | 9   6     8    | 3  4   2   |
+------------------+----------------+------------+
| 289    1     489 | 5   234*  24*  | 7  68  36  |
| 5      3     6   | 78  19    79   | 18 2   4   |
| 28*    24*   7   | 38* 1234  6    | 5  9   13  |
+------------------+----------------+------------+
| 7      8     2   | 6   49    1    | 49 3   5   |
| 369    4569  1   | 2   3459  4579 | 49 67  8   |
| 369    4569  349 | 37  8     4579 | 2  167 167 |
+------------------+----------------+------------+

Not sure what this is, but the 5 * cells (containing 2348) form a pattern which eliminates 24 from r6c5 and solves the puzzle
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TomC



Joined: 30 Oct 2020
Posts: 144
Location: Wales

PostPosted: Sat Sep 18, 2021 6:39 am    Post subject: Reply with quote

And it can eliminate 2 and 4 from r4c13
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Mogulmeister



Joined: 03 May 2007
Posts: 966

PostPosted: Sat Sep 18, 2021 8:42 am    Post subject: Reply with quote



Nicely done Tom. One way of explaining this (others exist I am sure) is an ALS with two digit eliminations which is reasonably rare.

Set A {2,3,4,8}
Set B {2,3,4}


The restricted common digit is 3 (r4c5,r6c4)

The 2's and 4's in red can see all the other 2's and 4's in A & B so are eliminated. These are the common candidates.

Good spot!
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Mogulmeister



Joined: 03 May 2007
Posts: 966

PostPosted: Sat Sep 18, 2021 9:39 am    Post subject: Reply with quote

I guess you could also view this as a slightly unconventional WXYZ wing - the 4 candidates are in 5 cells.
You can view the <38> in r6c4 as a hinge.

If itís 3 then you create a <24> locked pair in r4c56 eliminating all the 2s and 4s in the red cells.

If itís 8 then r6c12 become 2 and 4 making the same eliminations as above.
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TomC



Joined: 30 Oct 2020
Posts: 144
Location: Wales

PostPosted: Sat Sep 18, 2021 9:59 am    Post subject: Reply with quote

Indeed, many ways to describe this.

My first thought was to say that if r6c5 is either 2 or 4 then r6c4 would always be 3 leading to a contradiction in box 5

I then noticed the other elimination of 24's in box 4
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Mogulmeister



Joined: 03 May 2007
Posts: 966

PostPosted: Sat Sep 18, 2021 10:50 am    Post subject: Reply with quote

Also a contradiction with the

ANP (24=3)r4c56-(3=8)r6c4 etc etc

Which puts a contradictory 3 in r4c9.
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