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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
PostPosted: Tue Feb 08, 2011 11:23 pm    Post subject: Wed Feb 9 VH Reply with quote
XY-Wing 58 89 59 pivoted in r7c1 eliminating 5 in r3c5 solves it.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Feb 09, 2011 4:41 am    Post subject: Reply with quote
As is often the case, these puzzles have a number of solutions.

An XY-Chain or Multi-Coloring sets r7c1<>8

Another XY-Chain sets r3c1<>8

A Type 3 UR (28) in boxes 78 establishes pincers, setting r1c2<>5
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada
PostPosted: Wed Feb 09, 2011 1:01 pm    Post subject: Reply with quote
An ER knocks off the <8> in R7C1.
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garytorborg



Joined: 19 Jan 2011
Posts: 28
PostPosted: Thu Feb 10, 2011 7:25 pm    Post subject: Reply with quote
cgordon wrote:
An ER knocks off the <8> in R7C1.


I'm not familiar with the term "ER". At the beginning of this thread, someone said there was an XY-wing pivoting on that same cell; at the moment, I have 589 (three candidates) in that cell. If it is "58," I can see the 59 pincer but not the 89 anywhere.

Help, anyone?
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Thu Feb 10, 2011 8:10 pm    Post subject: Reply with quote
garytorborg wrote:
cgordon wrote:
An ER knocks off the <8> in R7C1.


I'm not familiar with the term "ER". At the beginning of this thread, someone said there was an XY-wing pivoting on that same cell; at the moment, I have 589 (three candidates) in that cell. If it is "58," I can see the 59 pincer but not the 89 anywhere.

Help, anyone?

Gary,

In my grid in box 8, the only 5s are in row 7. Therefore, a 5 cannot exist in r7c1, leaving 89 as the pivot of the XY-Wing.

P.S. ER stand for the technique known as Empty Rectangle.

http://www.intosudoku.com/Doc/EmptyRectangles.html

Last edited by Marty R. on Thu Feb 10, 2011 8:13 pm; edited 1 time in total
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Thu Feb 10, 2011 8:12 pm    Post subject: Reply with quote
ER is "empty rectangle", also known as a "hinge".

After basics:
Code:
+----------------+----------------+----------------+
| 7    58   4    | 19   359  15   | 6    28   238  |
| 6    1    3    | 4    8    2    | 5    9    7    |
| 58#  9    2    | 7   3-5   6    | 4    1    38   |
+----------------+----------------+----------------+
| 1    3    9    | 6    7    4    | 28   28   5    |
| 4    7    5    | 3    2    8    | 9    6    1    |
| 2    6    8    | 5    1    9    | 3    7    4    |
+----------------+----------------+----------------+
| 89@  4    7    | 1289 59#  15   | 28   3    6    |
| 589  258  1    | 289  6    3    | 7    4    28   |
| 3    28   6    | 28   4    7    | 1    5    9    |
+----------------+----------------+----------------+

Keith
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