Proven Sudoku
Techniques / Exotic and rank-zero
Pattern Overlay Method
Also called POM, Template filtering, Pattern overlay.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
Every digit has to land in one of a fixed set of shapes across the grid. This method lists all the shapes that still fit, then keeps only the ones that work together. Anything no surviving shape uses can be ruled out. It is really a job for a computer.
The exact rule, for stronger players
The rule, stated exactly: For each digit, enumerate every valid placement pattern consistent with the givens. Discard patterns incompatible with any other digit's surviving patterns. Candidates absent from every surviving pattern are eliminated.
What it removes: Remove candidates that appear in no surviving template.
Why it works: Exhaustive over single-digit templates. Sound, and complete for the constraints considered.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- Forcing Chain (general form)Pick something and assume it.
Related exotic and rank-zero
- Rank TheoryA way to count a pattern.
- Senior ExocetA bigger version of the Exocet pattern, with more squares acting as the target.
- SK LoopA ring of almost complete sets passing through the corners of a band and a stack.
- Table-Driven MethodsWork out ahead of time what follows from each single guess, and store it in a table.
- Broken WingA ring of squares where one number would have nowhere to go if the ring were perfect.
How often does it come up?
Our rough estimate: a computational method rather than a hand technique. There are 46656 possible single-digit patterns before filtering.