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Thursday V Hard puzzle

 
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David



Joined: 02 Jun 2006
Posts: 58
Location: Bedford, UK

PostPosted: Thu Jun 08, 2006 6:25 pm    Post subject: Thursday V Hard puzzle Reply with quote

After filling in 12 relatively simple numbers to todays puzzle, I ended up with 235 and 35 as possibilities for R1C46, and 35 for both R9C46. Does this represent a unique rectangle ? (ie R1C4 has to be a 2) because the rectangle stretches over three blocks rather than two ??
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Thu Jun 08, 2006 6:42 pm    Post subject: Reply with quote

That's it! You are right on all counts.

Steve
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David



Joined: 02 Jun 2006
Posts: 58
Location: Bedford, UK

PostPosted: Thu Jun 08, 2006 7:44 pm    Post subject: Reply with quote

Many thanks, perhaps I am getting the hang of it.
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Thu Jun 08, 2006 8:54 pm    Post subject: Another solution Reply with quote

So far as I know, Sam is not yet publishing puzzles that "need" Unique Rectangles to solve.

This one can also be solved via two X-wings.

David: The constraint is that the corners of the Rectangle occupy only two boxes. That is true here.

Keith


Last edited by keith on Tue Jun 13, 2006 8:51 pm; edited 1 time in total
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Fri Jun 09, 2006 12:20 am    Post subject: Reply with quote

I used an X-Wing and a Type 1 rectangle. Whether either was "needed", I have no idea; I saw them, so I used them.
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sdtibbs



Joined: 08 May 2006
Posts: 6

PostPosted: Mon Jun 12, 2006 6:09 pm    Post subject: Reply with quote

I am really trying to understand how you arrive at possibilities of the cell's final number. Could you please explain why r1c4 has to be a two and not a 2 in r2c4. Can you not have 4 cells in the rectangle have the same pair combination ie 35 and if not why. Sad
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Mon Jun 12, 2006 9:05 pm    Post subject: Reply with quote

sdtibbs wrote:
I am really trying to understand how you arrive at possibilities of the cell's final number. Could you please explain why r1c4 has to be a two and not a 2 in r2c4. Can you not have 4 cells in the rectangle have the same pair combination ie 35 and if not why. Sad


I don't know anything about the placement of the "2", but as to the last question, the answer is no. This type of thing is a no-no:

Code:
35--35
------
------
------
35--35


This is called the "deadly pattern." Published puzzles are supposed to have just one unique solution. If you had the above, you could interchange the "3s" and "5s" and thus the puzzle would have more than one solution.

Keith explains it much better than me in his primer on Rectangles at:

http://www.sudoku.com/forums/viewtopic.php?p=29105#29105
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sdtibbs



Joined: 08 May 2006
Posts: 6

PostPosted: Tue Jun 13, 2006 12:48 pm    Post subject: Reply with quote

lor=darkblue][/color]
Thank you for the link. I have printed it and am studying this. Feel like I am back in school and love learning the process. Hope I can be on my own soon. Smile
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