Pattern Overlay / Template Method

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Pattern Overlay / Template Method

What It Is

Pattern Overlay (Template Method) enumerates all valid placements for a digit. Any cell filled in every pattern must take that digit; any cell unused in all patterns cannot take it. It’s systematic endgame logic.

When to Use

Extreme endgame when few digits remain and other techniques stall; practical with limited candidate positions.

How to Apply (Step-by-Step)

  1. Choose a target digit with few remaining spots.
  2. List all possible valid patterns placing that digit in required rows/cols/boxes.
  3. Overlay patterns: cells present in every pattern are placements; cells in no pattern are eliminations.
  4. Apply placements/eliminations.
  5. Repeat for other digits if needed.

If two template patterns remain for digit 7 and both place 7 in the same cell, set that cell to 7; if a cell appears in neither pattern, remove 7 from it.

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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