Proven Sudoku
Nishio Forcing Net
Also called Nishio Net, Forcing Net.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
The same check as Nishio. But you follow what happens in lots of directions at once, not just one line. It is strong. It is also very hard to do in your head.
The exact rule, for stronger players
The rule, stated exactly: Nishio extended to a branching net rather than a single chain, allowing multiple simultaneous implications from one assumption.
What it removes: Eliminate the assumed candidate on contradiction.
Why it works: As for Nishio, with a net of implications instead of a linear chain.
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
- NishioAssume a number goes in a square, then check whether the rest of that number can still fit everywhere it needs to.
Related chains
- 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.
- XY-ChainA chain of squares that each hold exactly two numbers.
- AIC with AHS NodesThe same as above but using sets of numbers that are hiding rather than sets of squares.
- AIC with ALS NodesA chain that can step through a small set of squares holding one more number than it has room for.
How often does it come up?
Our rough estimate: rare in hand solving.