Proven Sudoku
Dynamic Forcing Chain with Double Implication
Also called Double Implication Chain, Dynamic Double Forcing.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
Try both options for a square and follow each one out fully. Anything that turns out true both ways is true, whichever option is right.
The exact rule, for stronger players
The rule, stated exactly: Assume a candidate true and false in turn, propagate dynamically in each branch, and take any conclusion common to both.
What it removes: Apply the common conclusion.
Why it works: The two branches are exhaustive, so a shared conclusion is unconditional.
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
- Dynamic Forcing Chain with ContradictionAssume a digit is right.
Related chains
- Forcing Chain (general form)Pick something and assume it.
- Grouped AICA chain where a step can use a whole group of squares at once instead of a single square.
- KrakenTake a pattern that nearly works.
- NishioAssume a number goes in a square, then check whether the rest of that number can still fit everywhere it needs to.
- Nishio Forcing NetThe same check as Nishio.
How often does it come up?
Our rough estimate: powerful and unsatisfying in equal measure.