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Jul 20 VH

 
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kent7618



Joined: 15 Jun 2012
Posts: 8
PostPosted: Thu Jul 19, 2012 4:43 pm    Post subject: Jul 20 VH Reply with quote
Code:

+--------------+------------------+------------+
| 48  9   2    | 1468  148   16   | 35  7   35 |
| 478 38  3457 | 458   3458  9    | 6   2   1  |
| 1   6   35   | 2     7     35   | 8   4   9  |
+--------------+------------------+------------+
| 2   138 37   | 156   159   4    | 579 568 58 |
| 6   5   9    | 7     2     8    | 1   3   4  |
| 478 18  47   | 3     159   16   | 579 568 2  |
+--------------+------------------+------------+
| 9   2   1    | 458   6     35   | 345 58  7  |
| 3   7   8    | 9     45    2    | 45  1   6  |
| 5   4   6    | 18    138   7    | 2   9   38 |
+--------------+------------------+------------+


XY-Wing 58 35 38 pivoted in r7c8; r9c5<>3, r2c5=3, solves it.
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
PostPosted: Thu Jul 19, 2012 11:52 pm    Post subject: Jul 20 VH Reply with quote
After the Basics
Code:

+--------------+--------------+------------+
| 48  9   2    | 1468 148  16 | 35  7   35 |
| 478 38  3457 | 458  3458 9  | 6   2   1  |
| 1   6   35   | 2    7    35 | 8   4   9  |
+--------------+--------------+------------+
| 2   138 37   | 156  159  4  | 79  568 58 |
| 6   5   9    | 7    2    8  | 1   3   4  |
| 478 18  47   | 3    *159  16 | 79  *568 2  |
+--------------+--------------+------------+
| 9   2   1    | 458  6    35 | 345 -58  7  |
| 3   7   8    | 9    *45   2  | 45  *1   6  |
| 5   4   6    | 18   138  7  | 2   9   38 |
+--------------+--------------+------------+
Also Sashimi Finned X-Wing in row 68; r7c8<>5.
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Rocky Mozell



Joined: 28 Jul 2010
Posts: 34
Location: Boston, MA
PostPosted: Tue Jul 24, 2012 2:59 pm    Post subject: Reply with quote
I just used a 345 XYZ wing.
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kent7618



Joined: 15 Jun 2012
Posts: 8
PostPosted: Wed Jul 25, 2012 6:16 am    Post subject: Reply with quote
458 xyz wing can also be used.
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smc



Joined: 03 Aug 2012
Posts: 4
PostPosted: Fri Aug 03, 2012 3:45 pm    Post subject: unique rectangle Reply with quote
Is this really a valid puzzle? I don't how it can be, with the 2's and 4's forming a unique rectangle in B-4, B-8, and C-4, C-8. ~smc
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Fri Aug 03, 2012 5:00 pm    Post subject: Re: unique rectangle Reply with quote
smc wrote:
Is this really a valid puzzle? I don't how it can be, with the 2's and 4's forming a unique rectangle in B-4, B-8, and C-4, C-8. ~smc


Welcome to the forum. I don't understand where the UR is. I don't see any 2s in the boxes and columns listed. But the puzzle is valid.
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smc



Joined: 03 Aug 2012
Posts: 4
PostPosted: Sat Aug 04, 2012 12:31 am    Post subject: unique rectangle Reply with quote
Thanks for the welcome, Marty. Just making sure we're talking about the July 20 Very Hard puzzle. In row B, column 4, there is a 4, and in column 8, there is a 2. Then, in row C, column 4, there is a 2, and in column 8, a 4, which was a given. I had originally had 458 as the possibles for B4, but ruled out 4 because that would result in a unique rectangle. I kept hitting snags, and finally found that 4 is the correct answer for that cell. Why is this OK?
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Aug 04, 2012 12:50 am    Post subject: Reply with quote
Smc,

Below is an example or a UR, or, more accurately, a Deadly Pattern (DP), so called because it's an invalid solution because the numbers can be interchanged, leading to two solutions to what is supposed to be a puzzle with a unique solution.

A DP cannot contain a given because there is no interchangeability. Hope this is clear enough.

Code:

+-------+--------+--------+
| . . . | .  . . | . .  . |
| . . . | 24 . . | . 24 . |
| . . . | 24 . . | . 24 . |
+-------+--------+--------+
| . . . | .  . . | . .  . |
| . . . | .  . . | . .  . |
| . . . | .  . . | . .  . |
+-------+--------+--------+
| . . . | .  . . | . .  . |
| . . . | .  . . | . .  . |
| . . . | .  . . | . .  . |
+-------+--------+--------+

Play this puzzle online at the Daily Sudoku site
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