Can Swordfish use boxes as well as rows and columns?

Post the puzzle or solving technique that's causing you trouble and someone will help

Can Swordfish use boxes as well as rows and columns?

Postby bat999 » Sat Jan 31, 2015 5:41 pm

Hi
I saw a blog post that said something like...
"by the way, do you know that Swordfish can use boxes? Not just rows and columns"

I can't find the post now. :evil:

Does anybody here know about this technique? :?

If it's true, please explain and show an example. :)

Or provide a link to some internet documentation about it. 8-)
8-)
User avatar
bat999
2017 Supporter
 
Posts: 674
Joined: 15 September 2014
Location: UK

Re: Can Swordfish use boxes as well as rows and columns?

Postby JasonLion » Sat Jan 31, 2015 6:11 pm

There is a swordfish like pattern that uses blocks instead of some/all of the rows/columns, but it is not called a swordfish.

Lookup MutantFish, for example here. The logic is essentially the same as for a swordfish, but they are a fair bit harder to spot in a puzzle.
User avatar
JasonLion
2017 Supporter
 
Posts: 621
Joined: 25 October 2007
Location: Silver Spring, MD, USA

Re: Can Swordfish use boxes as well as rows and columns?

Postby Leren » Sat Jan 31, 2015 7:56 pm

Hi bat. Fish that use boxes as well as rows and columns are known as Franken or Mutant. You can learn all about Fish on this site here http://forum.enjoysudoku.com/the-ultimate-fish-guide-t4993.html known as the ultimate fish guide
but, as like many other topics on this site, it's a hard slog through a very extensive topic. An easier way is to type franken or mutant in the search box, and you'll see discussion of examples or discussion as they come up in daily puzzles and so on, perhaps a more easy way to digest the information a bit at a time. Here is a link to the Hodoku site that has a fairly basic coverage of the topic, but it has graphical worked examples and may be useful.

http://hodoku.sourceforge.net/en/tech_fishc.php

Leren
Leren
 
Posts: 2842
Joined: 03 June 2012

Re: Can Swordfish use boxes as well as rows and columns?

Postby bat999 » Sat Jan 31, 2015 9:37 pm

OK, thanks.
Not so straightforward, what! :shock:
8-)
User avatar
bat999
2017 Supporter
 
Posts: 674
Joined: 15 September 2014
Location: UK

Re: Can Swordfish use boxes as well as rows and columns?

Postby rjamil » Sat Oct 31, 2015 7:43 pm

Hi,

While I am reading Swordfish technique for learning/understanding, found this site.

Here Swordfish example given for candidate 3 in Examples B. stated that, "We can eliminate 3 as candidate in every cell marked in blue." (Where only rows marked in blue.)

In Example C, stated that, "In any case, each of the rows 2, 4, 6 and 8, must contain a 3 in one of the colored cells, so no other cell in those rows can contain a 3." (But the same condition also applies to columns 2, 4, 6 and 8 too.)

My question is, why eliminate candidate 3 from rows 2, 4, 6 and 8 only? Why not from columns 2, 4, 6 and 8 as well?

Edit: get it.
From here, as stated, "When 2 Rows contain only 2 candidates each, and candidates are located in the Same two columns, you may eliminate all other candidates from these 2 columns."

Similarly, when 2 columns contain only 2 candidates each, and candidates are located in the same two rows, you may eliminate all other candidates from these 2 rows.

R. Jamil
rjamil
 
Posts: 121
Joined: 15 October 2014
Location: Karachi, Pakistan


Return to Help with puzzles and solving techniques