W-Wing

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W-Wing

What It Is

W-Wing uses two non-intersecting {x,y} bi-value cells connected by a strong link on one candidate. The chain forces one endpoint to be y, so any cell seeing both endpoints cannot take y.

When to Use

Advanced stage with many bi-value pairs; when coloring or XY-Wings fail and you spot matching pairs not seeing each other.

How to Apply (Step-by-Step)

  1. Identify two identical pairs {x,y} in different rows/columns/boxes.
  2. Find a strong link on x (or y) bridging units that connect to each pair.
  3. Form the chain: pair A – strong link – connector – strong link – pair B.
  4. Eliminate y (the non-linked candidate) from any cell that sees both pairs.
  5. Simplify and re-scan.

Two {3,7} cells not seeing each other plus a strong link on 3 between their units force one of them to be 7; eliminate 7 from cells seeing both.

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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