ExpertUsefulness: Low
Swordfish
An X-Wing scaled to three rows and three columns. A candidate confined to three shared columns across three rows is eliminated elsewhere in those columns.
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Three rows confine a candidate to three shared columns; it's cleared elsewhere in them.
patterneliminatesolved
How to spot it
- 1Find three rows where a candidate appears in two or three cells.
- 2Verify all those cells fall within the same three columns.
- 3Eliminate the candidate from the rest of those columns.
When to use
On expert puzzles when X-Wings and chains don't crack it.
When not to
If a shorter chain achieves the same elimination, prefer it — swordfish are error-prone by hand.
Common mistake
Requiring exactly three cells per row. Two or three each is fine, as long as the columns align.