## A Fishing Question

Advanced methods and approaches for solving Sudoku puzzles

### A Fishing Question

I have been contemplating X-wings when one of the strong links is not in a row or column, but in a box. Along the way, I found this interesting specimen. It is the Daily Sudoku of Jan 15:
Code: Select all
`Puzzle: DS011507+-------+-------+-------+| . 7 6 | . 9 . | . 8 . | | . . 2 | . . 3 | . . 9 | | . 3 . | 6 . . | . . . | +-------+-------+-------+| 1 . . | 5 . . | . . . | | . 6 9 | . 2 . | 4 3 . | | . . . | . . 6 | . . 8 | +-------+-------+-------+| . . . | . . 1 | . 5 . | | 6 . . | 2 . . | 8 . . | | . 2 . | . 5 . | 1 7 . | +-------+-------+-------+`

Basic moves will get you to this sticking point:
Code: Select all
`DS011507+----------------+----------------+----------------+| 5    7    6    | 4    9    2    | 3    8    1    | | 48   148  2    | 78   178# 3    | 5    6    9    | | 9    3    18c  | 6    18C  5    | 7    4    2    | +----------------+----------------+----------------+| 1    48   348# | 5    348b 9    | 6    2    7    | | 78   6    9    | 1    2    78B  | 4    3    5    | | 2    45   3457 | 37   347  6    | 9    1    8    | +----------------+----------------+----------------+| 478  9    478# | 38   6    1    | 2    5    34   | | 6    15   15   | 2    37   47   | 8    9    34   | | 3    2    48a  | 9    5    48A  | 1    7    6    | +----------------+----------------+----------------+`

I believe the intended way forward is an XY-wing, but I have marked an interesting fishy thingy.

It is actually a swordfish on <8>, the strong links (conjugate pairs) are aA, bB, and cC. aA is in R9, bB is in B5, and cC is in R3. The usual swordfish logic applies, and the eliminations are in the cells marked #.

Can anyone tell me the name of this creature, and provide more insights or point me to discussions?

Thank you,

Keith
keith
2017 Supporter

Posts: 215
Joined: 03 April 2006

### re: A Fishing Question

keith wrote:
Code: Select all
`+----------------+----------------+----------------+| 5    7    6    | 4    9    2    | 3    8    1    | | 48   148  2    | 78   178# 3    | 5    6    9    | | 9    3    18c  | 6    18C  5    | 7    4    2    | +----------------+----------------+----------------+| 1    48   348# | 5    348b 9    | 6    2    7    | | 78   6    9    | 1    2    78B  | 4    3    5    | | 2    45   3457 | 37   347  6    | 9    1    8    | +----------------+----------------+----------------+| 478  9    478# | 38   6    1    | 2    5    34   | | 6    15   15   | 2    37   47   | 8    9    34   | | 3    2    48a  | 9    5    48A  | 1    7    6    | +----------------+----------------+----------------+`

It is actually a swordfish on <8>, the strong links (conjugate pairs) are aA, bB, and cC. aA is in R9, bB is in B5, and cC is in R3. The usual swordfish logic applies, and the eliminations are in the cells marked #.

Can anyone tell me the name of this creature, and provide more insights or point me to discussions?

yes, it is a Franken Swordfish rrb\ccc:
r39b5\c356

Pat

Posts: 3674
Joined: 18 July 2005

Keith wrote:It is actually a swordfish on <8>, ...

I see it as a continuous nice loop:

[r3c3]=8=[r3c5]-8-[r4c5]=8=[r5c6]-8-[r9c6]=8=[r9c3]-8-[r3c3], => r2c5/r4c3/r7c3<>8.

Carcul
Carcul

Posts: 724
Joined: 04 November 2005