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VH 3rd December

 
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Mogulmeister



Joined: 03 May 2007
Posts: 1040

PostPosted: Fri Dec 03, 2021 9:05 am    Post subject: VH 3rd December Reply with quote

Code:

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

Play this puzzle online at the Daily Sudoku site
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Mogulmeister



Joined: 03 May 2007
Posts: 1040

PostPosted: Fri Dec 03, 2021 9:08 am    Post subject: Reply with quote

After basics
Code:
+--------------+-----------------+--------------+
| 46  3   5    | 478  9    478   | 1   2   68   |
| 469 47  479  | 48   2    1     | 3   5   68   |
| 2   1   8    | 5    3    6     | 4   9   7    |
+--------------+-----------------+--------------+
| 148 2   47   | 678  1578 578   | 68  3   9    |
| 189 78  6    | 3789 4    378   | 2   17  5    |
| 3   5   79   | 6789 178  2     | 68  17  4    |
+--------------+-----------------+--------------+
| 7   48  3    | 1    58   4589  | 59  6   2    |
| 58  6   1    | 2    578  5789  | 59  4   3    |
| 45  9   2    | 34   6    345   | 7   8   1    |
+--------------+-----------------+--------------+
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 658
Location: Rimini, Italy

PostPosted: Fri Dec 03, 2021 10:16 am    Post subject: Reply with quote

Hi everyone,

first step W-Wing 5,8 in r7c5,r8c1 SL with number 5 in r9c16 and -8 in r7c2,r8c56

and XY-Wing 1,7,9 in r5c18,r6c3 and -7 in r6c8

Ciao Gianni
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Earl



Joined: 30 May 2007
Posts: 664
Location: Victoria, KS

PostPosted: Fri Dec 03, 2021 12:43 pm    Post subject: Dec 03 VH Reply with quote

(Correction)
My first step before the 179 xywing was:
458xywing@R7C2, -5R9C6

Early Earl


Last edited by Earl on Fri Dec 03, 2021 4:10 pm; edited 2 times in total
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Mogulmeister



Joined: 03 May 2007
Posts: 1040

PostPosted: Fri Dec 03, 2021 12:49 pm    Post subject: Reply with quote

Hi Earl - good spot.
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Mogulmeister



Joined: 03 May 2007
Posts: 1040

PostPosted: Fri Dec 03, 2021 4:35 pm    Post subject: Reply with quote

Another way to look at this is to see that we have an almost XY wing - the killer <179> as used above.

However, at the start that is spoiled by the extra 8 in r5c1.

Code:
Either the 8 at r5c1 is true or the <179> XY Wing is true.

Let's look at making that 8.

r5c1 = 8 then r8c1 = 5 r9c1 = 4 and r7c2 = 8
                           |  |
                           |  |
                          \    /
                           \  /
                            \/
                           r9c4=3 and r9c6 = 5 and r7c5 = 8

Two 8's in row 7 - contradiction so we know that r5c1 can NOT be 8

The XY Wing <179> is true and puzzle solved.
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