What is this technique called?

Advanced methods and approaches for solving Sudoku puzzles

What is this technique called?

Postby 999_Springs » Sat Jul 14, 2007 7:59 pm

I haven't been posting for a while because I have had exams and I have also been away for some time. Anyway, I'm back, and while I was away I found this technique. I wouldn't call it "new" because there seem to be hundreds of fish experts who came to these forums earlier than I did, so it is certain they have found it already.

Suppose you have two columns in the same 3x9 block and they have the same three places for a particular candidate. Now add to that a strong link, one end of which sees a candidate in each of these two columns, thus:

Code: Select all
...|...|X.X
...|.X--+X.
...|...||.|
---+---+|-|
...|...||.|
...|.*.|X.X
---+---+|-|
...|...||.|
...|.*.|X.X

Possibilities in the places with asterisks may be eliminated.


What is this called, and how common is it?
Once upon a time I was a teenager who was active on here 2007-2011
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Re: What is this technique called?

Postby ronk » Sat Jul 14, 2007 9:39 pm

999_Springs wrote:
Code: Select all
...|...|X.X
...|.X--+X.
...|...||.|
---+---+|-|
...|...||.|
...|.*.|X.X
...|...||.|
---+---+|-|
...|...||.|
...|.*.|X.X
...|...||.|
Possibilities in the places with asterisks may be eliminated.


What is this called, and how common is it?

To be consistent with The Ultimate FISH Guide, it would be called a sashimi mutant swordfish (r2c79\r58b3 plus fin r2c5). No idea how common it might be. [edit: added link]
Last edited by ronk on Sat Jul 14, 2007 8:34 pm, edited 1 time in total.
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Postby daj95376 » Sat Jul 14, 2007 11:45 pm

The initial layout seemed to be shy on cells. After filling in, I see ...

Code: Select all
# two Empty Rectangles [r2c8b6] and [r2c8b9]
 *-----------------------*
 | . . . | . . . | X . X |
 | - - - | - X - | - X - |
 | . . . | . . . | - . - |
 |-------+-------+-------|
 | . . . | . . . | - . - |
 | . . . | . * . | X . X |
 | . . . | . . . | - . - |
 |-------+-------+-------|
 | . . . | . . . | - . - |
 | . . . | . * . | X . X |
 | . . . | . . . | - . - |
 *-----------------------*
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Empty Rectangle = finned Mutant X-wing

Postby Pat » Sun Jul 15, 2007 7:54 am

daj95376 wrote:two Empty Rectangles -- r2c8b6 and r2c8b9


thanks, daj95376, that reduces it to fish of order 2

( with the same fin at r2c5 )
  • r2b6\r5c8
  • r2b9\r8c8
( the information about r3c79 isn't needed )

Code: Select all
 *-----------------------*
 | . . . | . . . | . . . |
 | / / / | / # / | / X / |
 | . . . | . . . | . . . |
 |-------+-------+-------|
 | . . . | . . . | / X / |
 | . . . | . * . | X X X |
 | . . . | . . . | / X / |
 |-------+-------+-------|

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