Swordfish Technique
advancedExtension of X-Wing to three rows and columns
Swordfish extends the X-Wing concept to three rows and three columns.
Understanding the Concept
A candidate appears 2-3 times in exactly three rows, confined to the same three columns.
Forms a 3x3 pattern (though not all 9 positions need to be filled).
The candidate can be eliminated from all other cells in those three columns.
Can also work with three columns affecting three rows.
Named after the fish due to the shape of typical patterns.
Much rarer than X-Wing but follows the same logic.
Examples
Swordfish Pattern
If digit 5 in rows 1, 4, and 7 only appears in columns 2, 5, and 8, then 5 can be eliminated from all other cells in columns 2, 5, and 8.
Pro Tips
- •Start by finding rows with a candidate in only 2-3 positions
- •Check if three such rows use the same three columns
- •Swordfish patterns are quite rare
- •Usually indicates a very hard puzzle
