X-Wing

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X-Wing

What It Is

An X-Wing forms when two rows each have a candidate in exactly two columns, and those columns match. The four cells form a rectangle; each involved column will contain that candidate in one of those rows, so other cells in those columns lose that candidate.

When to Use

Middle to end game after intermediate techniques; scan one digit at a time when progress stalls.

How to Apply (Step-by-Step)

  1. Choose a candidate digit and scan rows for its remaining columns.
  2. Find two rows with exactly two options each in the same columns.
  3. Verify the rectangle: the four cells are the corners.
  4. Eliminate in columns: remove the candidate from other cells in those columns.
  5. Recheck for new singles or patterns.

If 5 appears only in columns 2 and 7 of both rows 4 and 8, eliminate 5 from all other cells in columns 2 and 7; the X-Wing clears the block.

See also

Scanning / Cross-Hatching Single Candidate (Naked Single) Single Position (Hidden Single) Naked Pairs / Triples / Quads Hidden Pairs / Triples / Quads Pointing Pairs / Triples (Locked Candidates Type 1) Box–Line Reduction (Locked Candidates Type 2) X-Wing Swordfish Jellyfish XY-Wing XYZ-Wing W-Wing Alternating Inference Chains (AICs) Forcing Chains / Forcing Nets Nishio Coloring Multi-Coloring Uniqueness Techniques (Unique Rectangle etc.) Fish Variants (Finned X-Wing, Sashimi etc.) ALS Techniques (ALS-XZ, ALS Chains) Sue de Coq Pattern Overlay / Template Method
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