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Puzzle 11/06/13: B XY (BBDB?)

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Mon Jun 13, 2011 3:52 pm    Post subject: Puzzle 11/06/13: B XY (BBDB?) Reply with quote

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

Play this puzzle online at the Daily Sudoku site
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Tue Jun 14, 2011 7:29 am    Post subject: Reply with quote

Two steps - I'll stick my neck out that the first move is a finned mutant swordfish?! On the basis that it has a fin, uses a block and is a step-up from an x-wing!
Quote:
(2)r1c7=r3c8 - r7c8=finned-x-wing(2)r2r7 ; r1c4<>2
m-wing-like(28) ; (2=5)r7c1-(5=8)r7c9 - r8c7=(8-2)r1c7=r1c2 ; r2c1<>2
(This is after much pruning - as lots of other moves in the grid at start)
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Tue Jun 14, 2011 2:35 pm    Post subject: Reply with quote

peterj wrote:
I'll stick my neck out that the first move is a finned mutant swordfish?

Although there are finned mutant Swordfish for your elimination, I think there's a finned Franken Swordfish that's closest to your description.

BTW, Your elimination could also be described as:

Kraken X-Wing r27\c14 w/direct fin cell r2c6 and indirect/Kraken fin cell r7c8

Regards, Danny
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Tue Jun 14, 2011 4:08 pm    Post subject: Reply with quote

daj95376 wrote:
Although there are finned mutant Swordfish for your elimination, I think there's a finned Franken Swordfish that's closest to your description.

Danny, what's the difference between "mutant" and "franken" - I have read Sudopedia but don't understand it Confused , largely I suspect because I am rather vague on this whole base set/cover set terminology.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Tue Jun 14, 2011 8:27 pm    Post subject: Reply with quote

Peter,

Here are the Swordfish patterns for your elimination. The information is cryptic, but still useful.

Code:
3-Fish r27b3\c148     fF 201\030  <> 2  r1c4   (finned Franken Swordfish)
3-Fish r27b3\c18b2    fF 201\021  <> 2  r1c4   (finned Franken Swordfish)
-and-
3-Fish r27b3\r1c18    fm 201\120  <> 2  r1c4   (finned mutant  Swordfish)
3-Fish r27c7\c14b9    fm 210\021  <> 2  r1c4   (finned mutant  Swordfish)
3-Fish r27c7\c1b29    fm 210\012  <> 2  r1c4   (finned mutant  Swordfish)
3-Fish r27c7\r1c1b9   fm 210\111  <> 2  r1c4   (finned mutant  Swordfish)

Note: base sectors are to the left of the "\", and cover sectors are to the right of the "\".

Franken Fish:
    Do not allow rows and columns to be present (together) on either side of the "\".

    One side of the "\" must contain at least one box.

    The presence of rows and columns isn't required, but it makes sense that only one side of the "\" can contain only boxes.

Mutant Fish:
    Rows and columns are present together on at least one side of the "\".

The principle of base sectors vs. cover sectors is not complex. Unfortunately, the details seem to be spread throughout the FISH threads. I had considered writing a basic thread on FISH, but decided that it would still be a serious undertaking. Given the (probably) limited number of people that are still reading the various forums for information, it didn't seem worthwhile.

A note for the nit-pickers. Sashimi patterns are labelled finned in the above output. I was satisfied with "finned".

Regards, Danny

Addendum: Do you want me to add a message about how base and cover sectors work?
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Tue Jun 14, 2011 8:44 pm    Post subject: Reply with quote

I missed the "fish fest" and ended up with a four stepper........

anp(28=5)r1c27-r2c1=r7c1-(5=8)r7c9; r1c9<>8
anp(28=3)r93c2-(3=8)r2c3; r1c2<>8
Coloring (8)
skyscraper (2)r9c26; r1c4,r2c1<>2

Ted
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Tue Jun 14, 2011 9:05 pm    Post subject: Reply with quote

My solver's default solution for this puzzle contained numerous steps ... ending in a 5-cell XY-Chain. It was intended to strain your solving techniques!

Regards, Danny
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Marty R.



Joined: 12 Feb 2006
Posts: 5127
Location: Rochester, NY, USA

PostPosted: Wed Jun 15, 2011 4:43 am    Post subject: Reply with quote

XY-Wing (258), flightless with transport; r1c2, r2c9<>8
XY-Wing (582); r7c8, r8c2<>2 + transport; r1c7<>2
Remote Pairs (25); r7c4<>2
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Wed Jun 15, 2011 7:37 am    Post subject: Reply with quote

daj95376 wrote:
Rows and columns are present together on at least one side of the "\"

OK. So I think basically what I have been thinking of as "Mutant" is in fact "franken" - the real "mutant" with mixed rows/columns is probably not one I will naturally spot!
daj95376 wrote:
Addendum: Do you want me to add a message about how base and cover sectors work?

It's one of these concepts that you read about think you understand ... but it's like sand in your fingers.. (I've read the xsudo pages twice at least)
Working your examples, I am pretty clear on "base sets" - they are candidate sets in houses which are constrained to an cardinality equal or less than the order of the fish i.e 3 or less in a house for a swordfish.
Cover sets I have a sort of intuitive grasp of from basic fish - and the conclusion that you can eliminate candidates not in intersection of the base and cover set.
So in your first example intuitively those are the cover sets, but in the second one why is b2 a cover set?
Thanks!
[EDIT] Actually reading this back and comparing with what I have read, I can see some of my confusion is around what they are "sets" of.. I describe it above as if they are sets of candidate cells, but actually they are sets of "constraints" (essentially "houses"). That makes more sense ... I might be close to a Doh! moment...
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Wed Jun 15, 2011 3:46 pm    Post subject: Reply with quote

peterj wrote:
[EDIT] Actually reading this back and comparing with what I have read, I can see some of my confusion is around what they are "sets" of.. I describe it above as if they are sets of candidate cells, but actually they are sets of "constraints" (essentially "houses").

Yes, to properly understand what's happening, you must work with the concept of "sets of houses/sectors/units" ... and the fact that one cell in each house/sector/unit of the base set must be true!
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