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Yet another one from 1sudoku

 
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sun Oct 02, 2016 12:14 am    Post subject: Yet another one from 1sudoku Reply with quote

I couldn't see today's puzzle from this site either. I hope it gets fixed soon. I'm sure that Sam will get right on it - especially seeing how much I've praised him in the past. Confused Anyway, I decided to do another 'Evil' puzzle from 1sudoku.com instead. I had trouble with it - but finally ended up finding a one-stepper. (I don't think it can be solved using just wings. Correct me if I'm wrong.)
Code:

 1sudoku.net #528188 Evil
 +-------+-------+-------+
 | . . 3 | . 5 . | . . 9 |
 | . . 4 | . 7 9 | . 1 . |
 | . 7 . | 8 . . | . . 4 |
 +-------+-------+-------+
 | 9 . . | . . . | . 6 . |
 | 1 . 5 | . . . | 8 . 2 |
 | . 8 . | . . . | . . 7 |
 +-------+-------+-------+
 | 3 . . | . . 8 | . 5 . |
 | . 5 . | 1 4 . | 9 . . |
 | 7 . . | . 6 . | 3 . . |
 +-------+-------+-------+
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JC Van Hay



Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

PostPosted: Sun Oct 02, 2016 3:56 am    Post subject: Reply with quote

Code:
+-------------+-----------------------+---------------+
| 26  1   3   | 246      5       246  | 7    8     9  |
| 8   26  4   | 236      7       9    | 256  1     35 |
| 5   7   9   | 8        12(3)   126  | 26   2(3)  4  |
+-------------+-----------------------+---------------+
| 9   23  7   | 2345     8       1245 | 145  6     35 |
| 1   36  5   | 3469     9-3     7    | 8    349   2  |
| 4   8   26  | 2569(3)  129(3)  1256 | 15   9(3)  7  |
+-------------+-----------------------+---------------+
| 3   49  16  | 7        29      8    | 24   5     16 |
| 26  5   268 | 1        4       3    | 9    7     68 |
| 7   49  18  | 259      6       25   | 3    24    18 |
+-------------+-----------------------+---------------+
XWing(3R36)-3r5c5; stte
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sun Oct 02, 2016 1:14 pm    Post subject: Reply with quote

I'm confused JC. That's obviously not a 'pure' X Wing (of which I'm sure you're aware). I see that you even enclosed the 3 in r6c4 in parens but I also see that your logic works. What is this type of X Wing called and how far can one extend this logic? Thanks, Don.
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Thu Oct 06, 2016 5:16 pm    Post subject: Yet another one from 1sudoku Reply with quote

dongrave wrote:
I'm confused JC. That's obviously not a 'pure' X Wing (of which I'm sure you're aware). I see that you even enclosed the 3 in r6c4 in parens but I also see that your logic works. What is this type of X Wing called and how far can one extend this logic? Thanks, Don.
We can call it a skyscraper with grouped node.
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JC Van Hay



Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

PostPosted: Thu Oct 06, 2016 7:00 pm    Post subject: Reply with quote

Don,

Finned XWing but more generally the definition of an XWing should be the following :
XWing : the solutions of the set C of all the candidates of a single digit in 2 units exclude a non-empty set X of candidates.
In a latin square : C is made up of the 4 candidates at the intersection of 2 rows and 2 columns [pure(?) Xwing]
In a sudoku : there are more "patterns" in the 4 boxes at the intersection of 2 rows of boxes and 2 columns of boxes. They are also respectively called XWing and 2-stringed kite as in the following examples with the greatest number of candidates as possible :
Code:
-1 1 1 | 1 1 1 or -1 1 1 | 1 1 1 or -1 1 1 | 1 1 1
-1 1 1 | 1 1 1    -1 1 1 | 1 1 .     1 1 1 | 1 1 .
 1 1 1 | 1 . .     1 1 1 | 1 1 .     1 1 1 | 1 1 .
 -------------     -------------     -------------
 1 1 1 | 1 1 1     1 1 1 | 1 1 1     1 1 1 | 1 1 1
 1 1 1 | 1 1 1     1 1 . | 1 1 .     1 1 1 | 1 1 1
 1 . . | 1 . .     1 1 . | 1 1 .     1 . . | 1 1 .

 C=XWing{1R36}     C=XWing{1C36}     C=Kite{1R6, 1C6}
 X={1r12c1}        X={1r12c1}        X={1r1c1}
How to find them ? In the 4 boxes in question, just enumerate the solutions from either a bilocal in 2 boxes or from an almost locked candidates.

Notes : with less candidates in the 4 boxes,
1. the number of exclusions can change,
2. a lot of other particular names are given to the XWing but they are of no interest to find the exclusion(s)!

JC
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Marty R.



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

PostPosted: Sat Oct 08, 2016 9:41 pm    Post subject: Reply with quote

Code:

+-----------+-----------------+------------+
| 26 1  3   | 246   5    246  | 7   8   9  |
| 8  26 4   | 236   7    9    | 256 1   35 |
| 5  7  9   | 8     123  126  | 26  23  4  |
+-----------+-----------------+------------+
| 9  23 7   | 2345  8    1245 | 145 6   35 |
| 1  36 5   | 3469  39   7    | 8   349 2  |
| 4  8  26  | 23569 1239 1256 | 15  39  7  |
+-----------+-----------------+------------+
| 3  49 16  | 7     29   8    | 24  5   16 |
| 26 5  268 | 1     4    3    | 9   7   68 |
| 7  49 18  | 259   6    25   | 3   24  18 |
+-----------+-----------------+------------+

Play this puzzle online at the Daily Sudoku site

(5=1)r6c7-r6c56=r4c6-(1=263)r3c678-(3=5)r2c9=> -5r4c9
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