## How is this a swordfish?

Advanced methods and approaches for solving Sudoku puzzles

### How is this a swordfish?

Simple Sudoku tells me that you can do a swordfish on the 1 candidates here but i don't see it. Not unless you can have 0 cells in one of the rows.
It could be that I'm just tired right now and it'll all get clearer in the morning, but could someone please take a look at it?
Just copy this into Simple Sudoku to get a good view.
Thanks /Joel

9..|...|...
.2.|6.4|..7
..5|..2|...
-----------
1..|9.6|37.
..7|.3.|2..
.63|7.8|..9
-----------
...|4..|9..
8..|2.5|.6.
...|...|..4

9.4|...|6..
328|6.4|..7
6.5|..2|...
-----------
182|946|375
497|531|286
563|728|..9
-----------
...|4..|9..
849|2.5|.63
...|..9|..4

[9] [1] [4] [1] [1] [] [6] [1] [1]
[3] [2] [8] [6] [1] [4] [1] [1] [7]
[6] [1] [5] [1] [] [2] [] [] [1]
[1] [8] [2] [9] [4] [6] [3] [7] [5]
[4] [9] [7] [5] [3] [1] [2] [8] [6]
[5] [6] [3] [7] [2] [8] [1] [1] [9]
[] [] [1] [4] [] [] [9] [1] [1]
[8] [4] [9] [2] [1] [5] [1] [6] [3]
[] [] [1] [1] [1] [9] [1] [1] [4]
reallyjoel

Posts: 8
Joined: 14 July 2005

### Re: How is this a swordfish?

reallyjoel wrote:Simple Sudoku tells me that you can do a swordfish on the 1 candidates here but i don't see it.

Look at rows 2,6 & 8 .
angusj

Posts: 306
Joined: 12 June 2005

gee as I said, it was just the lack of sleep that made me miss it.. right npw, I'm having trouble with a Normal Sudoku.. =) I really should sleep
reallyjoel

Posts: 8
Joined: 14 July 2005

Angus,

In thisthread I've seen this definition of a swordfish
IJ wrote:Look for N columns (2 for X-wing, 3 for the Swordfish, 4 for a Jellyfish, 5 for a Squirmbag) with only two candidate cells for a given digit (4 in this example). If these fall on exactly N common rows, and each of those rows has at least 2 candidate cells, then all N rows can be cleared of that digit (except it the defining cells!).

Row two of this puzzle has three cells with 1 as a candidate - have you been able to relax or refine the above definition somehow? What logic are you using?
Last edited by simes on Sun Dec 11, 2011 9:35 am, edited 1 time in total.
simes

Posts: 324
Joined: 11 March 2005
Location: UK

simes wrote:Row two of this puzzle has three cells with 1 as a candidate - have you been able to relax or refine the above definition somehow? What logic are you using?

It was briefly discussed here.

X-Wing is the dual of naked/hidden pairs.
Swordfish is the dual of naked/hiddne triplets.
Jellyfish is the dual of naked/hidden quadruples.

The initial definitions that were given for Swordfish and Jellyfish were unnecessarily restrictive. There is no need to limit the candidates to two per row.
Nick70

Posts: 156
Joined: 16 June 2005