Swordfish
A height's candidate cells across three rows (or columns) line up in the same three columns (or rows) — eliminate it everywhere else in those columns or rows.
How it works
- 1An X-Wing widened to three rows. Follow height 2 across the top three.
- 2Row 1 allows it in columns 1 and 2, row 2 in columns 2 and 3, row 3 in columns 1 and 3 — no row uses all three, but between them they never leave columns 1, 2 and 3.
- 3Three rows each need a 2, and only three columns can supply one. Those three columns are fully booked.
- 4Strike 2 from every other cell in columns 1, 2 and 3.
- 5The rows do NOT have to use two columns each, and they don't have to be the same two — that's the trap. All that matters is that their combined columns number three.
- Height ruled out
- Relationship — The arrow shows which cells support the deduction.
- Conclusion — The final arrow lands beside the proved or ruled-out height.