The New Sudoku Players' Forum

[tlanglet]

I agree with Danny's comments. When I first started working with "almost" conditions, I proceeded based on posts by "Storming Norman" who used the terms "np" and "hp". Thus I have always viewed them as potential naked and hidden patterns; I have never viewed an almost naked pair as an ALS. Originally, I used the specific notation ANP/ANT to indicate the specific number of digits in the possible naked set, but have recently started using the more general terms ANS/AHS. Consistent, unambiguous notation is the key.

Ted

[David P Bird]

These recent exchanges go some way towards demonstrating a point I've repeatedly made before. Anyone trying to pick up solving methods by reading our solutions will be confused by our lack of consistency in our terms and notations. It's clear that many contributors here aren't very concerned about this, but I would point out that we hope that these readers that will provide tomorrow's contributors as our membership rolls over. We would do well to keep this in mind and try to recall the difficulties we had in mastering the jargon.

To reiterate:
An Almost Naked Set is a set of N cells containing N+1 candidates
The internal link in the set is strong as no two member candidates can both be false

An Almost Hidden Set is a set of N cells containing N-1 locked candidates.
The internal link in the set is weak as no two unlocked candidates can both be true.

Both these conditions can be described as ALSs needing one further digit to be resolved to become fully locked, hence that term is ambiguous.

A set of N cells with N-1 locked candidates out of a total of N+1 will have two unlocked candidates that are conjugately linked, just as in a bivalue cell. Whether the set is viewed as an AHS or ANS depends on whether the link is taken to be weak or strong.

Finally, AHSs and ANSs form complementary partitions of the unresolved cells in a house – one of the unlocked digits must be true in the AHS and all the others in the ANS. Consequently it's usually possible to navigate an AIC through either set to reach the same eliminations.

[ArkieTech]

Both these conditions can be described as ALSs needing one further digit to be resolved to become fully locked, hence that term is ambiguous.

A set of N cells with N-1 locked candidates out of a total of N+1 will have two unlocked candidates that are conjugately linked, just as in a bivalue cell. Whether the set is viewed as an AHS or ANS depends on whether the link is taken to be weak or strong.

Thanks David,

Most helpful!

[Luke]

ALS is dead, and no one told me! Shouldn't there be a funeral?? After all these years, I should send flowers at the very least ...

[ronk]

ALS is dead, and no one told me! Shouldn't there be a funeral?? After all these years, I should send flowers at the very least ...

LOL, IMO few would attend the funeral! AFAIK only tlanglet and proponent David P Bird are using ANS in place of the historical ALS.