quasi-finned Swordfish

Advanced methods and approaches for solving Sudoku puzzles

quasi-finned Swordfish

Postby daj95376 » Tue Oct 03, 2006 3:50 pm

Code: Select all
4 . . . . . . . 9
. . . . 7 . . . .
. . 3 4 . 2 8 . .
. . 1 . . 9 6 . .
. 8 . . 3 . . 7 .
. . 2 5 . . 4 . .
. . 5 6 . 1 3 . .
. . . . 8 . . . .
9 . . . . . . . 2     # Arabian Star from Claudia


# after SSTS
 *-----------------------------------------------------------------------------*
 | 4      -12567  *678     | 138     156     3568    |*1257    12356   9       |
 | 12568   1256    689     | 1389    7       3568    | 125     123456  13456   |
 | 1567    15679   3       | 4       1569    2       | 8       156     1567    |
 |-------------------------+-------------------------+-------------------------|
 | 357     3457    1       | 78      24      9       | 6       2358    358     |
 | 56      8       469     | 12      3       46      | 1259    7       15      |
 | 367     3679    2       | 5       16     #78      | 4       1389    138     |
 |-------------------------+-------------------------+-------------------------|
 | 278     247     5       | 6       29      1       | 3       489     478     |
 |-12367  -123467 *467     | 29      8      *3457    |*1579    1456   -14567   |
 | 9      -13467  *678     |+37      45     *3457    |*157     14568   2       |
 *-----------------------------------------------------------------------------*

I'm not up on my finned fish, but the asterisk (*) cells seem to form a Swordfish in <7> with a quasi-fin (#). However, since the quasi-fin is not in a box with another member of the Swordfish, it appears that nothing can be derived using the standard definition of a finned fish. But, the relationship [r6c6]-7-[r4c4]=7=[r9c4] exists. This causes [r9c2]<>7 and reduces the Swordfish to an X-Wing. The final result is the same eliminations as the original Swordfish -- excluding [r9c4]. I called it a quasi-finned Swordfish in another posting. Does it have another name ... or an equivalent technique?

In a finned fish relationship, (I believe) one looks for an overlap to derive common eliminations. In a quasi-finned fish relationship, eliminations are prevented.
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Postby Myth Jellies » Tue Oct 03, 2006 5:55 pm

Nothing better than discovering this stuff on your own.

Here is a link with similar deductions and further links

http://forum.enjoysudoku.com/viewtopic.php?t=4731

(Havard, Mike Barker, and others added some stuff since the last time you posted to it, daj.)
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Postby Havard » Tue Oct 03, 2006 6:21 pm

[EDIT: Said wrong stuff.]
Last edited by Havard on Tue Oct 03, 2006 3:48 pm, edited 1 time in total.
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Postby ronk » Tue Oct 03, 2006 7:38 pm

[edit: no longer a reason for the original post]
Last edited by ronk on Tue Oct 03, 2006 3:55 pm, edited 1 time in total.
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Postby Havard » Tue Oct 03, 2006 7:47 pm

oops, I'm sorry. Getting late. Thanks for pointing out my mistake!:)
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Postby daj95376 » Tue Oct 03, 2006 8:14 pm

Actually there are two overlapping, finned Jellyfish for <7> that're more appropriate for the eliminations I indicated.

Code: Select all
 *-----------------------------------------------------------------------------*
 | 4      -12567   678     | 138     156     3568    | 1257    12356   9       |
 | 12568   1256    689     | 1389    7       3568    | 125     123456  13456   |
 |*1567   *15679   3       | 4       1569    2       | 8       156    *1567    |
 |-------------------------+-------------------------+-------------------------|
 |*357    *3457    1       |#78      24      9       | 6       2358    358     |
 | 56      8       469     | 12      3       46      | 1259    7       15      |
 |*367    *3679    2       | 5       16     #78      | 4       1389    138     |
 |-------------------------+-------------------------+-------------------------|
 |*278    *247     5       | 6       29      1       | 3       489    *478     |
 |-12367  -123467  467     | 29      8       3457    | 1579    1456   -14567   |
 | 9      -13467   678     | 37      45      3457    | 157     14568   2       |
 *-----------------------------------------------------------------------------*

Jellyfish [r3467c1249] for <7>, Fin: [r6c6]=7 => Swordfish [r347c129] -or-
Jellyfish [r3467c1269] for <7>, Fin: [r4c4]=7 => Swordfish [r367c129]


Another interpretation:

Code: Select all
Double Implication Chain for <7> in [b5]

[r4c4]=7 => Swordfish [r367c129]
[r6c6]=7 => Swordfish [r347c129]


Note: Claudia has produced multiple Arabian-Star puzzles as of this message. This is the first and shouldn't be confused with the KILLER Jellyfish version mentioned elsewhere.
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