Technique
When You Need an Swordfish
Swordfish handles cases where an X-Wing almost works but the digit has a third possible cell. It is one of the last purely pattern-based techniques before chain logic takes over.
At a glance
Swordfish at a Glance
- Technique
- Swordfish
- Difficulty level
- Advanced
- Also known as
- three-row X-Wing
- First needed on
- Expert puzzles
How to spot it
How to Spot an Swordfish
Find three rows in which a digit has two or three candidate cells, and check whether all of them fall inside the same three columns. The rows do not each need all three columns — two of the three is enough.
Common mistake
The Mistake Solvers Make
Requiring exactly three candidates per row. Two is fine. What matters is that the union of all candidate columns across the three rows is no more than three columns.
Practice
Practise This Technique
Expert puzzles are where the swordfish first becomes necessary. Generate a free printable expert Sudoku PDF and work through a few.
More techniques
Other Sudoku Techniques
- Naked Single — beginner
- Hidden Single — beginner
- Naked Pair — intermediate
- Pointing Pair — intermediate
- X-Wing — advanced
FAQ
Swordfish — Frequently Asked Questions
What is an swordfish in Sudoku?
A swordfish is the three-row version of an X-Wing. A digit is confined to at most three cells in each of three rows, and all those cells fall within the same three columns. The digit must take one cell in each row, so it can be eliminated from those three columns everywhere else.
How do you find an swordfish?
Find three rows in which a digit has two or three candidate cells, and check whether all of them fall inside the same three columns. The rows do not each need all three columns — two of the three is enough.
Is the swordfish a beginner or advanced technique?
It is an advanced technique. Swordfish handles cases where an X-Wing almost works but the digit has a third possible cell. It is one of the last purely pattern-based techniques before chain logic takes over.