Proven Sudoku
Grouped AIC
Also called Grouped Alternating Inference Chain, Grouped chain, AIC with grouped nodes.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
A chain where a step can use a whole group of squares at once instead of a single square. Groups make chains reach further, and the rules for following them are the same.
The exact rule, for stronger players
The rule, stated exactly: An AIC in which a node may be a set of candidates of one digit confined to the intersection of two houses, treated as a single unit that is true if any member is true.
What it removes: As for AIC, with grouped endpoints treated as units.
Why it works: A group behaves exactly like a single candidate for inference purposes: it is true if any member holds the digit, and a house-mate of every member is weakly linked to the whole group.
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
- Alternating Inference ChainA chain that switches between two kinds of step.
- Locked Candidates (general form)Sometimes all the spots for a digit inside one group also sit inside a second group.
Related chains
- 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.
- Unit Forcing ChainTake one number in one row, column or box and try each home it could have.
- X-ChainA chain about one number only.
How often does it come up?
Our rough estimate: common in hard solving. Grouping is what makes many chains reachable at all.