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arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Wed Feb 01, 2012 1:48 pm Post subject: best way to solve this one is get started

pattern game by joel64 Oct 12, 2010

Code:

*-----------*
|...|..1|..2|
|..3|.4.|.5.|
|.2.|6..|4..|
|---+---+---|
|..2|...|..1|
|.7.|.8.|.4.|
|6..|...|5..|
|---+---+---|
|..5|..3|.8.|
|.4.|.7.|6..|
|1..|9..|...|
*-----------*

SudoQ

Joined: 02 Aug 2011
Posts: 127

Posted: Wed Feb 01, 2012 2:52 pm Post subject:

Nice one stepper! I like puzzles when not only singles are needed after the first step. /SudoQ

Marty R.

Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

Posted: Wed Feb 01, 2012 6:10 pm Post subject:

I didn't fare so well. I used multi-coloring a few times and a Finned X-Wing before a quad was exposed which finished it off.

JC Van Hay

Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

Posted: Wed Feb 01, 2012 6:39 pm Post subject:

3 givens for a single digit on a "diagonal" => look for a (Finless, Finned or Sashimi) Swordfish. Here ... Sashimi Swordfish(6R257) : -6r4c5.r9c6; stte

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Wed Feb 01, 2012 7:11 pm Post subject:

I believe this is an L-wing

Code:

*--------------------------------------------------------------------*
| 45789 5689 46789 | 3578 359 1 | 3789 3679 2 |
| 789 a189-6 3 | 278 4 2789 | 1789 5 6789 |
| 5789 2 1789 | 6 359 5789 | 4 1379 3789 |
|----------------------+----------------------+----------------------|
| 34589 3589 2 | 3457 3569 45679 | 3789 3679 1 |
| 359 7 19 | 1235 8 2569 | 239 4 369 |
| 6 b1389 1489 | 12347 c1239 2479 | 5 2379 3789 |
|----------------------+----------------------+----------------------|
| 279 e69 5 | 124 d126 3 | 1279 8 479 |
| 2389 4 89 | 1258 7 258 | 6 1239 359 |
| 1 368 678 | 9 256 24568 | 237 237 3457 |
*--------------------------------------------------------------------*
L-wing
(1)r2c2=(1)r6c2-(1)r6c5=(1-6)r7c5=(6)r7c2 => r2c2<>6

JC Van Hay

Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

Posted: Wed Feb 01, 2012 11:51 pm Post subject:

arkietech wrote:

I believe this is an L-wing

Yes, an L2 (or H1) Wing. Furthermore and apparently, the only simplest 1-step wing besides "a" Swordfish on 6s! Wink

Luke451

Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California

Posted: Thu Feb 02, 2012 7:24 pm Post subject:

I saw just a singles chain at first.

Code:

*--------------------------------------------------------------------*
| 45789 5689 46789 | 3578 359 1 | 3789 3679 2 |
| 789 1689 3 | 278 4 2789 | 1789 5 6789 |
| 5789 2 1789 | 6 359 5789 | 4 1379 3789 |
|----------------------+----------------------+----------------------|
| 34589 3589 2 | 3457 3569 45679 | 3789 3679 1 |
| 359 7 19 | 1235 8 2569 | 239 4 369 |
| 6 1389 1489 | 12347 1239 2479 | 5 2379 3789 |
|----------------------+----------------------+----------------------|
| 279 69 5 | 124 126 3 | 1279 8 479 |
| 2389 4 89 | 1258 7 258 | 6 1239 359 |
| 1 368 678 | 9 256 24568 | 237 237 3457 |
*--------------------------------------------------------------------*

6's: r7c5=r7c2-r9c3=r1c3-r1c8=r2c9-r5c9=r5c6 ==>r4c5,r9c6<>6

Then I saw JC's solution had the same eliminations, and now I think I like the idea of the sashimi swordfish better. The singles chain is just the underlying mechanism and not as easy to spot as the pattern.

Would it be better to call it a finned sashimi swordfish? If so, the only direct elimination would be (6)r9c6.

Adding:
I may be just confusing myself, but now I think I see just a finned swordfish in columns 358, fin (6)r7c5 that takes out (6)r9c6. I still see the row based fish as finned sashimi.

Last edited by Luke451 on Thu Feb 02, 2012 7:53 pm; edited 1 time in total

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Thu Feb 02, 2012 7:52 pm Post subject:

Luke451 wrote:

Would it be better to call it a finned sashimi swordfish? If so, the only direct elimination would be (6)r9c6.

Why not call it a finned swordfish?

Code:

*--------------------------------------------------------------------*
| 45789 5689 *46789 | 3578 359 1 | 3789 *3679 2 |
| 789 1689 3 | 278 4 2789 | 1789 5 6789 |
| 5789 2 1789 | 6 359 5789 | 4 1379 3789 |
|----------------------+----------------------+----------------------|
| 34589 3589 2 | 3457 *3569 45679 | 3789 *3679 1 |
| 359 7 19 | 1235 8 2569 | 239 4 369 |
| 6 1389 1489 | 12347 1239 2479 | 5 2379 3789 |
|----------------------+----------------------+----------------------|
| 279 69 5 | 124 f126 3 | 1279 8 479 |
| 2389 4 89 | 1258 7 258 | 6 1239 359 |
| 1 368 *678 | 9 *256 2458-6 | 237 237 3457 |
*--------------------------------------------------------------------*
finned swordfish

Luke451

Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California

Posted: Thu Feb 02, 2012 7:55 pm Post subject:

Whoa, simultaneous posts! I just came to same conclusion, Dan. See addendum.

JC Van Hay

Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium

Posted: Thu Feb 02, 2012 9:22 pm Post subject:

Luke451 wrote:

Would it be better to call it a finned sashimi swordfish? If so, the only direct elimination would be (6)r9c6.

A Sashimi Fish is implicitly finned. Here 6R257 is a SSF "in the boxes" 5 AND 8 => the 2 eliminations. Wink

Further notes : to be clearer, here is the rule of thumb I am always using while pencilmarking :

3 givens for the same digit (but no 2 in the same line of boxes) AND no Locked Candidates for that digit => look if there are 2 bilocals in Columns(Rows) that can enter into a 3-SIS X Chain in Columns(Rows). IOW, there is no need to look for a fish of higher size or of a shape different from the basic one.

Here we have 3 such "Swordfishes" (2 Finned Swordfishes and 1 Sashimi Swordfish):

6C358 or 6r91c3 6r14c8 6r479c5 => -6r9c6
6C368 or 6r91c3 6r14c8 6r459c6 => -6r4c5
6R257 or 6r7c52 6r2c29 6r5c96 => -6r4c5.r9c6

Best regards, JC.

[edit : removal of typos]

Last edited by JC Van Hay on Fri Feb 03, 2012 9:16 am; edited 1 time in total

ronk

Joined: 07 May 2006
Posts: 398

Posted: Thu Feb 02, 2012 10:21 pm Post subject:

Swordfish, especially two simultaneous sashimi swordfish, simply can't beat the simplicity of an x-chain IMO. (6)r7c5=(6)r7c2 - (6)r2c2 = (6)r2c9 - (6)r5c9 = (6)r5c6 ==> r4c5,r9c6<>6

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Thu Feb 02, 2012 10:48 pm Post subject:

JC Van Hay wrote:

3 givens for the same digit (but no 2 in the same line of boxes) AND no Locked Candidates for that digit => look if there are 2 bilocals in Columns(Rows) that can enter into a 3-SIS X Chain in Columns(Rows). IOW, there is no need to look for a fish of higher size or of a shape different from the basic one.

Is this more basic than a finned swordfish? My problem is what I learned first is "more basic" than what I learn later. An example: xy-wing is more basic than a w-wing when the w-wing is much easier to spot.

Code:

*--------------------------------------------------------------------*
| 45789 5689 46789 | 3578 359 1 | 3789 3679 2 |
| 789 *1689 3 | 278 4 2789 | 1789 5 *6789 |
| 5789 2 1789 | 6 359 5789 | 4 1379 3789 |
|----------------------+----------------------+----------------------|
| 34589 3589 2 | 3457 359-6 *45679 | 3789 3679 1 |
| 359 7 19 | 1235 8 *2569 | 239 4 *369 |
| 6 1389 1489 | 12347 1239 2479 | 5 2379 3789 |
|----------------------+----------------------+----------------------|
| 279 *69 5 | 124 *126 3 | 1279 8 479 |
| 2389 4 89 | 1258 7 258 | 6 1239 359 |
| 1 368 678 | 9 *256 2458-6 | 237 237 3457 |
*--------------------------------------------------------------------*
Sashimi Swordfish

daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Sat Feb 04, 2012 5:52 pm Post subject:

Luke451 wrote:

Then I saw JC's solution had the same eliminations, and now I think I like the idea of the sashimi swordfish better. The singles chain is just the underlying mechanism and not as easy to spot as the pattern.

Would it be better to call it a finned sashimi swordfish? If so, the only direct elimination would be (6)r9c6.

Adding:
I may be just confusing myself, but now I think I see just a finned swordfish in columns 358, fin (6)r7c5 that takes out (6)r9c6. I still see the row based fish as finned sashimi.

Hmmm, where to start.

1) JC thinks in terms of advanced structures and truth sets. When it comes to fish patterns, it takes two fish -- ronk: "two simultaneous sashimi swordfish" -- to get both eliminations. I use to call this pattern a Siamese Sashimi Swordfish in order to list both eliminations as coming from one "fish". However, using just one fish and one elimination is sufficient to expose a Locked Candidate 1 for the companion elimination.

2) tarek, the originator (in another forum) of a thread on FISH, favors using "finned sashimi". This caused a revolt from ronk and myself who argued that finned was redundant when Sashimi was used. Now, I seldom check to see if a fish is actually Sashimi ... and simply call it finned.

3) If a fish pattern exists in rows, then there's often a complementary fish in the columns. The fish do not have to be of the same size. In this grid, the Sashimi Swordfish in the rows has a complementary finned Swordfish in the columns.

Regards, Danny

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Sat Feb 04, 2012 7:00 pm Post subject:

Quote:

3) If a fish pattern exists in rows, then there's often a complementary fish in the columns.

I believe a regular (unfinned) fish always has a complement.

Keith

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