The New Sudoku Players' Forum

by **Bud** » Mon Nov 10, 2008 6:55 am

First consider the X-wing. There are 3 almost X-Wing patterns that have been defined, the Color Wing (aka Skyscraper), the finned X-WIng, and the Sashimi X-Wing. But to my knowledge only two of these have been defined for the Swordfish. Here is a diagram of the missing almost 6 cell Swordfish which I am naming the Color Swordfish. If the candidate X in r1c9 were moved to r2c9, this would be a true Swordfish. The pattern is an AIC with the ends of the chain at r1c9 and r2c2. As such it is easy to show that if not X is at either end of the chain it forces the other end to be
X and therefore not X cannot be at both ends. This means that X must be either in r1c9 or r2c2 and cannot be in any cell which is a peer of bothe these cells. There is some flexibility in the number of cells that can be in the pattern. I will add this to this post unless I find out that someone else has covered this topict sometime or somewhere. I have used this so I do have examples which will take some time to find.

Color Swordfish Example

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

by **re'born** » Mon Nov 10, 2008 7:21 am

Hi Bud,

You should check the ultimate fish guide, but I think this is just a sashimi swordfish.
[Edit: Pat's post suggests that this should be 2 finned (or is it sashimi?) swordfish]

by **Pat** » Mon Nov 10, 2008 7:45 am

Bud wrote:Here is a diagram of the missing almost 6 cell Swordfish which I am naming the Color Swordfish.

The pattern is an AIC with the ends of the chain at r1c9 and r2c2. As such it is easy to show that if not X is at either end of the chain it forces the other end to be X and therefore not X cannot be at both ends. This means that X must be either in r1c9 or r2c2 and cannot be in any cell which is a peer of bothe these cells.

Color Swordfish Example
Code: Select all
|-----------------+-----------------+-----------------| | * - * | . - . | . . X | | . X . | . - . | * * - | | . - . | . - . | . . - | |-----------------+-----------------+-----------------| | . - . | . - . | . . - | | . - . | . X . | . . X | | . - . | . - . | . . - | |-----------------+-----------------+-----------------| | . - . | . - . | . . - | | . - . | . - . | . . - | | . X . | . X . | . . - | |-----------------+-----------------+-----------------|

this is 2 finned Swordfish --

c259/r159 ( fin=r2c2 ) gives the exclusions in r1b1
c259/r259 ( fin=r1c9 ) gives the exclusions in r2b3

by **aran** » Mon Nov 10, 2008 8:05 am

Or without resort to fishing tackle :
if either of the X's in the top band is present, the eliminations hold
and if neither is present, column 5 is emptied of X=> impossible

by **re'born** » Mon Nov 10, 2008 9:43 am

Pat wrote:
this is 2 finned Swordfish --
c259/r159 ( fin=r2c2 ) gives the exclusions in r1b1
c259/r259 ( fin=r1c9 ) gives the exclusions in r2b3

I've been away for some time and I've all but forgot everything I knew about fishy patterns. In the old days, if you had the fin, but were missing the candidate, wasn't it called sashimi? If so, did it get changed recently?

by **Glyn** » Mon Nov 10, 2008 9:55 am

re'born The way I see it is that to get the full set of eliminations needs two different swordfish and fin combos to be identified.

by **re'born** » Mon Nov 10, 2008 9:59 am

Glyn wrote:re'born The way I see it is that to get the full set of eliminations needs two different swordfish and fin combos to be identified.

I agree with that Glyn. What I'm curious about is why the individual finned swordfish aren't called sashimi swordfish (not that it matters much, I'm just curious).

by **Bud** » Mon Nov 10, 2008 12:12 pm

Thanks for the replies, Guys. Let me clarify what I am looking for. I'm trying to find out if anybody has documented this missing pattern before. Ib other words is it new. I don't need to know how it works since it is a 6 cell AIC and I understand the logic. I have included the patterns for a Sashimi Swordfish and a Finned Swordfish. Notice that the only cell eliminations are in the same box as the fins for these two. These patterns aren't missing.

Sashimi Swordfish Example

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

Finned Swordfish Example

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

by **ronk** » Mon Nov 10, 2008 12:16 pm

Bud wrote:I'm trying to find out if anybody has documented this missing pattern before.

Sorry if I missed it but ... missing from what :?:

by **tarek** » Mon Nov 10, 2008 12:55 pm

re'born wrote:I've been away for some time and I've all but forgot everything I knew about fishy patterns. In the old days, if you had the fin, but were missing the candidate, wasn't it called sashimi? If so, did it get changed recently?

It was suggested that adjectives to describe the "fin" staus and the "core degeneratin status" to be used seperately.

In the example, the sashimi fish are finned fish ... a better description wou;d then be sashimi finned fish.

tarek

by **Bud** » Mon Nov 10, 2008 1:08 pm

Hi Ron,
It definitely is missing from the advanced solving sites, although it is just as much an almost Swordfish pattern and just as useful as the finned and sashimi. All three almost X-wing patterns are documented. Why not document all 3 almost Swordfish patterns also?

by **tarek** » Mon Nov 10, 2008 1:15 pm

Bud,
Why are you calling the patterms "almost fish" ....

Why are you putting skyscrapers & colours in the same pot?

tarek

by **ronk** » Mon Nov 10, 2008 1:42 pm

Bud wrote:It definitely is missing from the advanced solving sites ...

Can you be more specific than that? (Preferably the site(s) that do include the swordfish you claim are "not missing".)

by **daj95376** » Mon Nov 10, 2008 1:42 pm

The Color Swordfish Example is the Swordfish equivalent of a Skyscraper.

A Skyscraper is the combined eliminations of two overlapping Sashimi X-Wings.

This is the combined eliminations of two overlapping Sashimi Swordfish.

It already has a name: Siamese Sashimi Swordfish.

by **Bud** » Mon Nov 10, 2008 1:52 pm

Thanks Daj,
That's exactly what I wanted to find out. This is the end of the post, I hope.

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