Sashimi Swordfish

Level 9 · Purple Belt

Strategy:

Finned & Sashimi Fish

Requires:

Finned Swordfish

Overview

Sashimi Swordfish is a Swordfish variant where one or more base cells are missing, compensated by fin cells. Eliminations target cells seeing both the fin and the cover set.

How It Works

Find an almost-Swordfish with one or more missing base candidates.
Fin cells in the same block compensate for the missing cells.
Eliminate the candidate from cells that see both the fin block and the cover columns.

Example

Look for Sashimi Swordfish.

Sudoku grid showing the initial puzzle state for Look for Sashimi Swordfish.

1

Sashimi Swordfish

Check digit 2 in rows 2, 3 and 8. These rows form a Swordfish pattern in columns 1, 4 and 8.

Sudoku grid illustrating step 1: Sashimi Swordfish — Check digit 2 in rows 2, 3 and 8. These rows form a Swordfish pattern in columns 1, 4 and 8.

2

Sashimi Swordfish

r2c2 is already filled with 1.

Sudoku grid illustrating step 2: Sashimi Swordfish — r2c2 is already filled with 1.

3

Sashimi Swordfish

Digit 2 cannot go in r2c3 because r7c3 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 3: Sashimi Swordfish — Digit 2 cannot go in r2c3 because r7c3 is already in this column. Remove the entry or choose a different digit.

4

Sashimi Swordfish

Digit 2 cannot go in r2c5 because r6c5 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 4: Sashimi Swordfish — Digit 2 cannot go in r2c5 because r6c5 is already in this column. Remove the entry or choose a different digit.

5

Sashimi Swordfish

r2c6 is already filled with 6.

Sudoku grid illustrating step 5: Sashimi Swordfish — r2c6 is already filled with 6.

6

Sashimi Swordfish

r2c7 is already filled with 9.

Sudoku grid illustrating step 6: Sashimi Swordfish — r2c7 is already filled with 9.

7

Sashimi Swordfish

r2c9 is already filled with 4.

Sudoku grid illustrating step 7: Sashimi Swordfish — r2c9 is already filled with 4.

8

Sashimi Swordfish

Digit 2 cannot go in r3c2 because r5c2 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 8: Sashimi Swordfish — Digit 2 cannot go in r3c2 because r5c2 is already in this column. Remove the entry or choose a different digit.

9

Sashimi Swordfish

Digit 2 cannot go in r3c3 because r7c3 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 9: Sashimi Swordfish — Digit 2 cannot go in r3c3 because r7c3 is already in this column. Remove the entry or choose a different digit.

10

Sashimi Swordfish

Digit 2 cannot go in r3c5 because r6c5 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 10: Sashimi Swordfish — Digit 2 cannot go in r3c5 because r6c5 is already in this column. Remove the entry or choose a different digit.

11

Sashimi Swordfish

Digit 2 is not a current candidate in r3c6 because earlier solving steps already removed it.

Sudoku grid illustrating step 11: Sashimi Swordfish — Digit 2 is not a current candidate in r3c6 because earlier solving steps already removed it.

12

Sashimi Swordfish

r3c7 is already filled with 6.

Sudoku grid illustrating step 12: Sashimi Swordfish — r3c7 is already filled with 6.

13

Sashimi Swordfish

Digit 2 cannot go in r3c9 because r1c7 is already in this box. Remove the entry or choose a different digit.

Sudoku grid illustrating step 13: Sashimi Swordfish — Digit 2 cannot go in r3c9 because r1c7 is already in this box. Remove the entry or choose a different digit.

14

Sashimi Swordfish

Digit 2 cannot go in r8c2 because r5c2 is in this column and r7c3 is in this box. Remove the entry or choose a different digit.

Sudoku grid illustrating step 14: Sashimi Swordfish — Digit 2 cannot go in r8c2 because r5c2 is in this column and r7c3 is in this box. Remove the entry or choose a different digit.

15

Sashimi Swordfish

r8c3 is already filled with 8.

Sudoku grid illustrating step 15: Sashimi Swordfish — r8c3 is already filled with 8.

16

Sashimi Swordfish

Digit 2 cannot go in r8c5 because r6c5 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 16: Sashimi Swordfish — Digit 2 cannot go in r8c5 because r6c5 is already in this column. Remove the entry or choose a different digit.

17

Sashimi Swordfish

Digit 2 cannot go in r8c7 because r1c7 is already in this column. Remove the entry or choose a different digit.

Sudoku grid illustrating step 17: Sashimi Swordfish — Digit 2 cannot go in r8c7 because r1c7 is already in this column. Remove the entry or choose a different digit.

18

Sashimi Swordfish

r8c9 is already filled with 6.

Sudoku grid illustrating step 18: Sashimi Swordfish — r8c9 is already filled with 6.

19

Sashimi Swordfish

One base row has extra candidates in box 8. That box is the fin, so this becomes a Sashimi Swordfish.

Sudoku grid illustrating step 19: Sashimi Swordfish — One base row has extra candidates in box 8. That box is the fin, so this becomes a Sashimi Swordfish.

20

Sashimi Swordfish

Because of the fin, only cells in box 8 that also lie in columns 1, 4 and 8 can lose digit 2.

Sudoku grid illustrating step 20: Sashimi Swordfish — Because of the fin, only cells in box 8 that also lie in columns 1, 4 and 8 can lose digit 2.

21

Sashimi Swordfish

These are the cells that see both the fish structure and the fin: r9c4.

Sudoku grid illustrating step 21: Sashimi Swordfish — These are the cells that see both the fish structure and the fin: r9c4.

22

Sashimi Swordfish

Remove 2 from: r9c4.

Sudoku grid illustrating step 22: Sashimi Swordfish — Remove 2 from: r9c4.

23

Result after applying the technique.

Sudoku grid showing the result after applying the technique

Tips & Patterns

Sashimi Swordfish combines the complexity of Swordfish with finned fish logic.
These are quite rare and hard to spot manually.