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22 Aug VH

 
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Wed Aug 22, 2007 1:10 pm    Post subject: 22 Aug VH Reply with quote

I used an xyz wing which is easy enough to spot cos after basic eliminations there's only one square left with 3 numbers.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Wed Aug 22, 2007 1:32 pm    Post subject: Reply with quote

Which means it was also a BUG+1, for those who don't find that technique objectionable.

Also saw a couple of XY-wings & W-wings that would do the trick.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Wed Aug 22, 2007 3:25 pm    Post subject: Reply with quote

I used a W-Wing which didn't appear to do much and I don't recall if it exposed the XY-Wing which finished the puzzle.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Wed Aug 22, 2007 6:28 pm    Post subject: Reply with quote

Quote:
I used an xyz wing which is easy enough to spot cos after basic eliminations there's only one square left with 3 numbers.


indeed. A "one trick pony" ...
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Wed Aug 22, 2007 8:41 pm    Post subject: Reply with quote

Quote:
Which means it was also a BUG+1, for those who don't find that technique objectionable.


I looked up BUGs and they're cool. Let me get it right eh!
A BUG means the grid can't be solved or that there are 2 solutions. A BUG situation means there are ONLY PAIRS left - and that there are two of each number in every row, column and box. So if you have ONE cell with THREE numbers it's a BUG+1. You can remove the number from that cell that will give a BUG situation (i.e. 2 Nos every row, col, box) - then put it back as the right answer - cos Sudoku.com promised that all puzzles can be solved with one solution.

I would have thought situations like that are rare - but then again one just occured. My only objection is the esoteric acronym. Bivalue Universal Grave indeed - I can think of a more appropriate Bug***** word.
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Wed Aug 22, 2007 9:30 pm    Post subject: Reply with quote

cgordon wrote:
You can remove the number from that cell that will give a BUG situation

Actually, two of the digits in that cell produce the BUG situation. You can immediately place the one digit that prevents the BUG. It is easy to spot: it is the only one of the three digits that occurs three times in the House. (Box, Column or Row, it doesn't matter which. Only one of the digits occurs three times in all three of these and that is the one you keep.)
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Thu Aug 23, 2007 7:56 am    Post subject: Forgotten the name of this Reply with quote

Code:

+-------------+---------+------------+
| 2   7   4   | 1  8 5  | 6   3  9   |
| 3   18  18  | 2  9 6  | 4   7  5   |
| 9   5   6   | 34 7 34 | 8   2  1   |
+-------------+---------+------------+
| 5   3   2   | 6  4 1  | 7   9  8   |
|  67  69  79 | 5  2 8  | 13  14 34  |
| 18  4   18  | 9  3 7  | 2   5  6   |
+-------------+---------+------------+
| 4   2   79  | 8  1 39 | 5   6   37 |
|  68  68 3   | 7  5 49 | 19  14 2   |
| 17  19  5   | 34 6 2  |  39 8  347 |
+-------------+---------+------------+

I reached the following position (hopefully not by a lucky error) and I half remember a move that says if every unsolved cell bar 1 is a double, then the triple can be solved as the number common to the strongly connected set.

Don't know if I have quoted the rules correctly, and I guess it only applies if there is no direct further move.

In any event I applied the rule and put a 3 in r9c9 since all the c9 set contains 3, and of course it then falls out!
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Thu Aug 23, 2007 3:50 pm    Post subject: Reply with quote

George, it's called the BUG+1 pattern. The trivalue cell needs to be solved with the number that appears three times. If that candidate were eliminated then the deadly BUG pattern would result.
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