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Unique solution?
http://www.calcudoku.org/forum/viewtopic.php?f=2&t=76
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Author:  jomapil  [ Mon Oct 03, 2011 11:19 am ]
Post subject:  Unique solution?

I read Patrick said the solution of a puzzle is unique.
But in the puzzle 12x12 of yesterday I arrived at the following point:

I have a pattern of 4 cells ( 2x2 ). The first cage ( first column ) is a 6- and the second cage ( second column ) is a 16x.
I arrived at the situation all the 4 cells have 28. So I have 2 solutions. Is this possible or it is an error of mine?

Author:  pnm  [ Mon Oct 03, 2011 11:56 am ]
Post subject:  Re: Unique solution?

jomapil wrote:
I have a pattern of 4 cells ( 2x2 ). The first cage ( first column ) is a 6- and the second cage ( second column ) is a 16x.
I arrived at the situation all the 4 cells have 28. So I have 2 solutions. Is this possible or it is an error of mine?

For reference, the 6- is at e3 and e4, the 16x at f3 and f4.
I'm thinking that the 2,8 for the 6- is incorrect...

Patrick

Author:  jomapil  [ Mon Oct 03, 2011 4:49 pm ]
Post subject:  Re: Unique solution?

Yes. It is my conviction that one of the two cages is wrong. But my doubt is that situation is always incorrect because it would take at two solutions, isn't it?


2 8 8 2
8 2 and 2 8

Author:  pnm  [ Mon Oct 03, 2011 5:38 pm ]
Post subject:  Re: Unique solution?

jomapil wrote:
Yes. It is my conviction that one of the two cages is wrong. But my doubt is that situation is always incorrect because it would take at two solutions, isn't it?

It is in fact the case that as soon as you see a "double pair" like that,
you know they can't both be there. Often that is a useful clue.

(let's say you have cages 2- and 10+ in a 6x6 (side by side),
so for the 10+ you have 6,4, and say for the 2- you have 6,4 and 5,3 as candidates,
then you'd know the 2- has to have 5,3)

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