The New Sudoku Players' Forum

[CORMONSE]

Hello I am new in the forum. I want to ask on a technique that I have heard called Jelly Fish and I have not been able to find information on her. Can somebody inform me?

[Shazbot]

go here or here and read up on X-wing and Swordfish.

X-wing is a grid of 2x2 (2 rows, 2 columns) that allows you to make eliminations. Swordfish is the same pattern over 3x3 (3 rows, 3 columns). Just extend it to a 4x4 and you have your Jellyfish. I've been pleasantly surprised to be able to use it on a number of puzzles (that probably could have been solved using easier methods, but it's a bit of a thrill).

[CORMONSE]

Thank you to provide me the information, the links are really useful.

[Jeff]

Interestingly, this grid has a pattern that can be viewed as a jelly fish, a swordfish or an x-wing.

[angusj]

http://www.smh.com.au/articles/2005/12/21/1135032067258.html

[sheila08]

Angus---WOW!!!!!!!

Sheila

[ronk]

Interestingly, this grid has a pattern that can be viewed as a jelly fish, a swordfish or an x-wing.

I see the x-wing and the jellyfish, but where is the swordfish?

[edit: Oh, never mind, I see it now.]

[sheila08]

The coordinates for the jellyfish and the swordfish are????

Sheila

[MCC]

Hi Sheila08

The swordfish in Jeff's grid is:

r3c5, r3c7
r6c3, r6c5, r6c7
r8c3, r8c5


The jellyfish, or its very nibbled remains, are highlighted by the blue cells.

MCC

[tso]

I had *thought* that jellyfish was never required for a 9x9 sudoku because there would always be a lesser fish -- either swordfish or x-wing.

This one *appears* to disprove this rule:

Code: Select all

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


The jellyfish is in 1s in rows 1, 3, 4 and 8.

Code: Select all

 
 +15  +15   2    | 3    8    9    | 7    6    4   
  4    3    9    | 6    7    12   | 125  15   8   
  6    8    7    |+12   5    4    |+12   9    3   
 ----------------+----------------+----------------
 +12   4    3    | 9    26   5    |+16   8    7   
  25   6    8    | 7    1    3    | 9    4    25   
  9    7    15   | 4    26   8    | 156  3    125 
 ----------------+----------------+----------------
  8    9    15   | 125  3    12   | 4    7    6   
  3   +15   6    |+15   4    7    | 8    2    9   
  7    2    4    | 8    9    6    | 3    15   15   
 

It can be solved other methods, coloring, etc. However Sudoku Susser set on default settings does find the jellyfish.

[QBasicMac]

I did eliminations, but was unable to proceed after that.

Mac

Code: Select all

+------------+------------+-------------+
| 15  15  2  | 3   8   9  | 7   6   4   |
| 4   3   9  | 6   7   12 | 25  15  8   |
| 6   8   7  | 12  5   4  | 12  9   3   |
+------------+------------+-------------+
| 12  4   3  | 9   26  5  | 16  8   7   |
| 25  6   8  | 7   1   3  | 9   4   25  |
| 9   7   15 | 4   26  8  | 56  3   125 |
+------------+------------+-------------+
| 8   9   15 | 25  3   12 | 4   7   6   |
| 3   15  6  | 15  4   7  | 8   2   9   |
| 7   2   4  | 8   9   6  | 3   15  15  |
+------------+------------+-------------+


[sweetbix]

You can proceed like this

1. XYwing = r6c3, r6c7, r4c7 => remove 1 from r4c1, r6c9

Code: Select all

+------------+------------+-------------+
| 15  15  2  | 3   8   9  | 7   6   4   |
| 4   3   9  | 6   7   12 | 25  15  8   |
| 6   8   7  | 12  5   4  | 12  9   3   |
+------------+------------+-------------+
| 12  4   3  | 9   26  5  |+16  8   7   |
| 25  6   8  | 7   1   3  | 9   4   25  |
| 9   7  +15 | 4   26  8  |+56  3   125 |
+------------+------------+-------------+
| 8   9   15 | 25  3   12 | 4   7   6   |
| 3   15  6  | 15  4   7  | 8   2   9   |
| 7   2   4  | 8   9   6  | 3   15  15  |
+------------+------------+-------------+

If r6c7=6 => then r4c7=1 and => r4c1 is not 1
If r6c7=5 => then r6c3=1 and => r4c1 is not 1
In the same way you can remove 1 from r6c9

2. BUG

Code: Select all

+------------+------------+-------------+
| 15  15  2  | 3   8   9  | 7   6   4   |
| 4   3   9  | 6   7   12 | 25  15  8   |
| 6   8   7  | 12  5   4  | 12  9   3   |
+------------+------------+-------------+
| 12  4   3  | 9   26  5  | 16  8   7   |
| 25  6   8  | 7   1   3  | 9   4   25  |
| 9   7   15 | 4   26  8  | 56  3  +125 |
+------------+------------+-------------+
| 8   9   15 | 25  3   12 | 4   7   6   |
| 3   15  6  | 15  4   7  | 8   2   9   |
| 7   2   4  | 8   9   6  | 3   15  15  |
+------------+------------+-------------+

If there is only one cell with three candidates, the correct number for that cell is the one that is in 3 cells in that cells row, column and box => r6c9 = 5