## The Missng Almost Swordfish Pattern

Advanced methods and approaches for solving Sudoku puzzles

### The Missng Almost Swordfish Pattern

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    .   |   .    .    -   | |-----------------+-----------------+-----------------| `
Last edited by Bud on Mon Nov 10, 2008 9:48 am, edited 1 time in total.
Bud

Posts: 56
Joined: 24 August 2008

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]
Last edited by re'born on Mon Nov 10, 2008 6:00 am, edited 1 time in total.
re'born

Posts: 551
Joined: 31 May 2007

### 2 finned Swordfish

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

Pat

Posts: 3797
Joined: 18 July 2005

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
aran

Posts: 334
Joined: 02 March 2007

### Re: 2 finned Swordfish

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?
Last edited by re'born on Mon Nov 10, 2008 5:57 am, edited 1 time in total.
re'born

Posts: 551
Joined: 31 May 2007

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.
Glyn

Posts: 357
Joined: 26 April 2007

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).
re'born

Posts: 551
Joined: 31 May 2007

### The Missng Almost Swordfish Pattern

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    .   |   .    .    -   | |-----------------+-----------------+-----------------| `
Bud

Posts: 56
Joined: 24 August 2008

### Re: The Missng Almost Swordfish Pattern

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
ronk
2012 Supporter

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Joined: 02 November 2005
Location: Southeastern USA

### Re: 2 finned Swordfish

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

tarek

Posts: 2983
Joined: 05 January 2006

### The Missng Almost Swordfish Pattern

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?
Bud

Posts: 56
Joined: 24 August 2008

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

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

tarek

tarek

Posts: 2983
Joined: 05 January 2006

### Re: The Missng Almost Swordfish Pattern

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".)
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

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.
daj95376
2014 Supporter

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Joined: 15 May 2006

### The Missng Almost Swordfish Pattern

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

Posts: 56
Joined: 24 August 2008