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Oct 7 VH

 
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Earl



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

PostPosted: Thu Oct 07, 2021 11:21 am    Post subject: Oct 7 VH Reply with quote

I needed two xywings - again!

789@R4C1, -8R8C3 and 139@R7C4, -9R9C4

Someone, please do it in one step?

Early Earl
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Mogulmeister



Joined: 03 May 2007
Posts: 1017

PostPosted: Fri Oct 08, 2021 2:00 am    Post subject: Reply with quote

Code:

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



Joined: 03 May 2007
Posts: 1017

PostPosted: Fri Oct 08, 2021 2:14 am    Post subject: Reply with quote

Code:
+--------------+---------------+--------------+
| 6   79  4    | 5   139  13   | 37  2   8    |
| 1   3   8    | 27  27   6    | 4   5   9    |
| 79  2   5    | 39  4    8    | 37  1   6    |
+--------------+---------------+--------------+
| 78  4   1    | 6   78   2    | 5   9   3    |
| 3   6   2    | 4   5    9    | 8   7   1    |
| 5   789 79   | 137 1378 13   | 6   4   2    |
+--------------+---------------+--------------+
| 2   178 37   | 13  6    4    | 9   38  5    |
| 4   19  39   | 8   139  5    | 2   6   7    |
| 89  5   6    | 239 239  7    | 1   38  4    |
+--------------+---------------+--------------+


After basics.

Hi Earl - I saw it this way:

Look at r8c5 - with r37c4 its part of an almost <139> XY wing but there is an extra 3 in r8c5.

If that 3 is FALSE then the XY wing solves the puzzle as r1c5, r9c4 <> 9

OR

If that 3 is TRUE then r8c3 = 9, r6c3 = 7 and r4c1 = 8 which also solves the puzzle


We don't care if the 3 is there or not.
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Mogulmeister



Joined: 03 May 2007
Posts: 1017

PostPosted: Wed Oct 20, 2021 8:28 pm    Post subject: Reply with quote

Footnote

A simple inspection shows that the 3 can't exist in r8c5.

If it did, you would have two 9's in block 7 at r8c3 and r9c1 and that would never do.
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