Empty Boxes - I

Everything about Sudoku that doesn't fit in one of the other sections

Postby JPF » Sun Oct 01, 2006 10:12 pm

udosuk wrote:
Red Ed wrote:Yes, it's just a long chain of naked singles.

r8c6-r8c2-r5c2-r4c1-r1c1-r3c3-r3c6-r1c4-r1c9-r2c7-r4c7-r5c9-r7c9-r9c8-r9c3-r7c3
Then it's a matter of proving an empty box is determined by 8 filled box...
(E.g. there is no possible deadly pattern left...)

Correct for the first part of the proof.
You should easily solve the second part if you read carefully this thread (Thanks to Red Ed).

JPF
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Three boxes just around the corner?

Postby claudiarabia » Mon Jul 21, 2008 11:19 pm

The best I could archive was this meager result:

Code: Select all
. . 1 . . 4 . . 6
. 2 8 9 . . 4 . .
7 . 3 . . . . 5 .
. . . . 7 5 2 . .
. . . . 3 . . . .
. . . 1 . 8 . 3 .
. . . . . . 7 6 5
. . . . . . . 8 .
1 . . . . . . . 9


Can somebody eliminate the 1 in r9c1?

With best wishes

Claudia
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Postby JPF » Tue Jul 22, 2008 9:02 am

It's impossible.
This pattern
Code: Select all
 x x x | x x x | x x x
 x x x | x x x | x x x
 x x x | x x x | x x x
-------+-------+-------
 . . . | x x x | x x x
 . . . | x x x | x x x
 . . . | x x x | x x x
-------+-------+-------
 . . . | . . . | x x x
 . . . | . . . | x x x
 . . . | . . . | x x x

doesn't have any valid puzzle.
Any puzzle with this pattern has at least 2 solutions.

see :
http://forum.enjoysudoku.com/viewtopic.php?p=17488#p17488
http://forum.enjoysudoku.com/viewtopic.php?p=30961#p30961

JPF
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