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NOV 10th VH

 
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Wed Nov 10, 2021 7:48 am    Post subject: NOV 10th VH Reply with quote

Code:

+-------+-------+-------+
| . . 7 | 9 6 . | 4 5 . |
| . . . | . . . | 1 9 . |
| . 2 . | . . . | . . 6 |
+-------+-------+-------+
| 5 . . | . 3 1 | . . . |
| . . . | 6 . 7 | . . . |
| . . . | 2 5 . | . . 8 |
+-------+-------+-------+
| 3 . . | . . . | . 1 . |
| . 5 9 | . . . | . . . |
| . 6 4 | . 9 5 | 3 . . |
+-------+-------+-------+
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Wed Nov 10, 2021 7:51 am    Post subject: Reply with quote

478 XY wing.
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Wed Nov 10, 2021 9:17 am    Post subject: Reply with quote

At this point in the puzzle the 478 XY wing reveals itself
Code:

+-------------+--------------+-------------+
| 8   1   7   | 9    6   23  | 4   5    23 |
| 46  34  356 | 3578 278 238 | 1   9    23 |
| 9   2   35  | 35   1   4   | 78  78   6  |
+-------------+--------------+-------------+
| 5   478 268 | 48   3   1   | 267 2467 9  |
| 24  9   238 | 6    48  7   | 5   234  1  |
| 467 347 1   | 2    5   9   | 67  3467 8  |
+-------------+--------------+-------------+
| 3   78  28  | 47   247 6   | 9   1    5  |
| 127 5   9   | 1378 278 238 | 268 268  4  |
| 12  6   4   | 18   9   5   | 3   28   7  |
+-------------+--------------+-------------+

Play this puzzle online at the Daily Sudoku site

But what struck me was that r7c5 <> 2 as then r5c5=4, r5c1=2 results in no 2's in box 7
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Wed Nov 10, 2021 11:42 am    Post subject: Reply with quote

Nice one. If you plug the 2 into r7c5 and follow that loop you also put a 2 in r7c3 giving two 2’s in row 7.

(2-47)r7c5=4r5c5-(4=2)r5c1-r89c1=2r7c3 contradiction
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TomC



Joined: 30 Oct 2020
Posts: 349
Location: Wales

PostPosted: Wed Nov 10, 2021 2:34 pm    Post subject: Reply with quote

Another way to look at this contradiction is to travel in a different direction

If r7c5=2 then r89c1=2, r5c1=4, r5c5=8 and no place for a 4 in c5
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Wed Nov 10, 2021 4:19 pm    Post subject: Reply with quote

Wrong (right) in so many ways !
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