Proven Sudoku
AIC with AHS Nodes
Also called AHS-AIC, Almost Hidden Set chain node.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
The same as above but using sets of numbers that are hiding rather than sets of squares. The chain steps through them the same way.
The exact rule, for stronger players
The rule, stated exactly: An AIC in which a node is an almost hidden set: n digits confined to n+1 cells in a house.
What it removes: As for AIC.
Why it works: An AHS with one cell removed becomes a hidden set. The dual of the ALS argument.
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
- AIC with ALS NodesA chain that can step through a small set of squares holding one more number than it has room for.
- Almost Hidden SetThe mirror image of an almost locked set.
Related chains
- Alternating Inference ChainA chain that switches between two kinds of step.
- Bowman's BingoPick a digit, assume it, and write out everything that follows until you either finish or hit a contradiction.
- Cell Forcing ChainTake one square and try each number it could hold.
- Continuous Nice LoopA loop where the reasoning closes back on itself with no weak spot.
- Digit Forcing ChainTake one number in one square.
How often does it come up?
Our rough estimate: uncommon. Most solvers use ALS nodes and never reach for the dual.