Hard technique · Technique Academy

Swordfish

A Swordfish is an X-Wing with a third arm: a digit confined to two or three cells in each of three rows, all within the same three columns. It is rarer, and quieter, than its cousin.

Professor Cryptic, the owl who teaches in the app
Professor Cryptic is thinking

The reasoning

Why does the Swordfish work?

However the digit is placed in those rows, it uses up all three columns, so no other cell in those columns can hold it. Strike it there. Rows and columns may be exchanged.

A worked example

What does the Swordfish look like on a real board?

Swordfish worked exampleA sudoku board with pencil marks. The Swordfish uses R3C6, R3C7, R3C5, R5C6, R5C7, R5C5, R7C6, R7C7, R7C5 and digit 3 (rows 3, 5, 7). The move strikes candidates 3 in R2C7, 3 in R4C7, 3 in R6C5, 3 in R8C7.31925674825762523548235939184251935235672374681357939351589372374693763535741286214353587949781623523583729614
The move strikes candidates 3 in R2C7, 3 in R4C7, 3 in R6C5, 3 in R8C7. Digit 3, rows 3, 5, 7.
  • Cells that form the pattern
  • Cells that lose a candidate
  • Struck digit: ruled out

Make it stick

How can you practise the Swordfish?

The Technique Academy in Cryptic gives every technique its own lesson and 5 practice boards that need exactly this move.

Get it onGoogle PlayPlay Cryptic on the web

Further reading: HoDoKu's page on this family of techniques.

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