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Jan 13 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 1110
Location: Dar es Salaam Tanzania

PostPosted: Wed Jan 12, 2011 10:45 pm    Post subject: Jan 13 VH Reply with quote

XY-Wing 58 56 68 Pivoted in r4c6 removing 8's in BOX 4 row 5 solves it.
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cgordon



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

PostPosted: Thu Jan 13, 2011 4:34 pm    Post subject: Reply with quote

x wing on 6
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Abarmard



Joined: 13 Jan 2011
Posts: 4

PostPosted: Thu Jan 13, 2011 6:31 pm    Post subject: Why remove 8? Reply with quote

c5r4 why remove 8?

Last edited by Abarmard on Thu Jan 13, 2011 6:45 pm; edited 3 times in total
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Abarmard



Joined: 13 Jan 2011
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PostPosted: Thu Jan 13, 2011 6:32 pm    Post subject: Or why remove 8? Reply with quote

I don't get the logic
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Clement



Joined: 24 Apr 2006
Posts: 1110
Location: Dar es Salaam Tanzania

PostPosted: Thu Jan 13, 2011 11:48 pm    Post subject: Jan 13 VH Reply with quote

Abarmard wrote
Quote:
I don't get the logic
After the basics, you have the following Grid
Code:

+--------------+------------+---------------+
| 1278 178 4   | 5  28  267 | 3   9    1268 |
| 5    178 3   | 68 9   267 | 126 4   1268  |
| 6    9   28  | 1  3   4   | 7   5   28    |
+--------------+------------+---------------+
| 178  2   58  | 3  18  56  | 9   167 4     |
| 189  4   589 | 68 7   256 | 126 126 3     |
| 3    17  6   | 24 124 9   | 5   8   127   |
+--------------+------------+---------------+
| 248  5   7   | 24 6   1   | 28  3   9     |
| 2489 6   289 | 79 24  3   | 128 127 5     |
| 29   3   1   | 79 5   8   | 4   267 267   |
+--------------+------------+---------------+
In the above Grid the pivot 56 is in r4c6. Now, give any value in the pivot,all the 8's in BOX 4 row 5 including r4c5 will go. Can you see the logic?
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Ema Nymton



Joined: 17 Apr 2009
Posts: 89

PostPosted: Fri Jan 14, 2011 12:22 pm    Post subject: Re: Jan 13 VH Reply with quote

.

It is the short hand.

Clement wrote:
Abarmard wrote
Quote:
I don't get the logic
After the basics, you have the following Grid
Code:

+--------------+------------+---------------+
| 1278 178 4   | 5  28  267 | 3   9    1268 |
| 5    178 3   | 68 9   267 | 126 4   1268  |
| 6    9   28  | 1  3   4   | 7   5   28    |
+--------------+------------+---------------+
| 178  2   A58 | 3  18  B56 | 9   167 4     |
| 189  4   589 | C687   256 | 126 126 3     |
| 3    17  6   | 24 124 9   | 5   8   127   |
+--------------+------------+---------------+
| 248  5   7   | 24 6   1   | 28  3   9     |
| 2489 6   289 | 79 24  3   | 128 127 5     |
| 29   3   1   | 79 5   8   | 4   267 267   |
+--------------+------------+---------------+
In the above Grid the pivot 56 is in r4c6. Now, give any value in the pivot,all the 8's in BOX 4 row 5 including r4c5 will go. Can you see the logic?


The alignment of ABC makes an '8' in r5c1 or r5c3 not possible because A becomes '5' and C becomes '6' and B = 0. Thus r5c4 can only be '8'.

Ema Nymton
.
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cgordon



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

PostPosted: Fri Jan 14, 2011 2:30 pm    Post subject: Reply with quote

This is an XY wing which consists of three numbers (568) aligned in the three possible pairs (56)(58)(68). The pivot (56) “sees” the two wings (58) and (68). Whether the pivot is a (5) or a (6) - one of the wings will be an (8). So remove any (8) that “sees” BOTH of the wings.


Code:
            
+--------+-------+-------+   
| . .  . | . . . | . . . |   
| . .  . | . . . | . . . |   
| . .  . | . . . | . . . |   
+--------+-------+-------+   
| .  . 58| . . 56| . . . |   
| X8 . X8|68 . . | . . . |   
| .  . . | . . . | . . . |   
+--------+-------+-------+   
| . .  . | . . . | . . . |   
| . .  . | . . . | . . . |   
| . .  . | . . . | . . . |
+--------+-------+-------+
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Abarmard



Joined: 13 Jan 2011
Posts: 4

PostPosted: Fri Jan 14, 2011 9:14 pm    Post subject: Thank you Reply with quote

Thanks very much Smile
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Abarmard



Joined: 13 Jan 2011
Posts: 4

PostPosted: Fri Jan 14, 2011 9:17 pm    Post subject: One more question Reply with quote

This is great. Simply put, how did you recognize that this situation can exist? by checking the numbers one by one?
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Ema Nymton



Joined: 17 Apr 2009
Posts: 89

PostPosted: Sun Jan 16, 2011 1:21 pm    Post subject: Re: One more question Reply with quote

.

Abarmard wrote:
This is great. Simply put, how did you recognize that this situation can exist? by checking the numbers one by one?



Sudoku, as played here is subtle. You will find powerful tried and true techniques to help come to a valid solution of posted puzzles. The players like to use shorthand references (flying skyscrapers with W-X-Y wings and backward twists etc.) to show off their laudable skills. The techniques work and can be applied to other Sudoku/Soduko style puzzles.


Ema Nymton
~@:o?
.
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