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Adam Guest
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Posted: Fri Feb 10, 2006 4:05 am Post subject: Hard 2/6/2006 Confused |
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Hey Guys-
Hope you can help me understand why this is the next move. Here's the puzzle
Code: | _ 1 _ 6 3 8 9 _ X
3 4 9 5 7 2 6 1 8
8 5 6 4 9 1 7 3 2
_ 6 _ _ 4 5 3 _ 1
5 9 _ 7 _ 3 _ _ _
4 3 _ _ 2 _ 5 8 _
9 7 5 3 _ _ _ _ _
_ 2 4 _ 5 7 _ _ 3
_ 8 3 2 _ _ _ _ _ |
Apparently the X is a 5. WHY!? What rule is this and can you explain how this rule works? I see that there's a pair rule, if that's in fact what allows you to get this number, can someone explain to me how this rule works? Thanks :-)
--Adam |
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tcdev
Joined: 09 Feb 2006 Posts: 5 Location: Sydney, Australia
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Posted: Fri Feb 10, 2006 6:55 am Post subject: |
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(X) is either (4/5)
Pair R5C9 & R7C9 (4/6)
So (X) cannot be 4, it must be 5.
Regards,
Mark |
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tcdev
Joined: 09 Feb 2006 Posts: 5 Location: Sydney, Australia
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Posted: Fri Feb 10, 2006 7:09 am Post subject: |
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I should probably explain... (I'm a newbie so please excuse my lack of proper sudoku lingo)
The 'Pairs Rule' as I understand it...
If you have 2 pairs in any row, column or 3X3 box, then no other square in that row/column/box can have either of those two numbers.
In your case, since there is a pair (4/6) in column 9, no other square in that column can be either 4 or 6.
Similarly, if you have 2 numbers that exist in only (the same) 2 squares in any given row, column or box, then you can eliminate any other candidate numbers in those two squares (leaving just the so-called 'pairs').
You can also extend this to triplets (3 squares) as well.
Regards,
Mark |
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alanr555
Joined: 01 Aug 2005 Posts: 198 Location: Bideford Devon EX39
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Posted: Tue Feb 21, 2006 2:52 am Post subject: |
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Code: |
This puzzle can be solved using Mandatory Pairs - although it proved
useful to have the "missing" profiles for the rows and columns.
Congruent subsets included:
Row 1: 27 and 45
row 5: 18 and 246.
Col 1: 16 and 257
In any event a solution was derived without recourse to deriving
the candidate profiles.
Alan Rayner BS23 2QT
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