Lost 60 minutes due to misinterpreting this in p2:
> *whenever* you generate a hash
The code initially only did the 2016 stretching for
the triplet hash, not the quintet hash. By doing it
to both, pt 2 is solved.
Not sure the lru cache actually speeds anything up.
Many on the subreddit used the approach to generate
the quintet first and look backwards 1000 times
for a matching quintet (since quintets are more
rare than triplets), this will most likely speed
things up.
Also, this solution do not store the found keys.
Many other solutions do, I believe this is some
presumptions.
Hard one, an infamous AoC puzzle according to
Reddit.
Apparently, this is a classic logic problem named
"Missionaries and cannibals", or "Jealous husbands".
Hard lessons:
- Always use set() for visited nodes during BFS.
- Always use collections.queue() to create to queue
traversals for BFS.
- itertools permutations(), combinations() and
pairwise() may look similar, but they are not.
- Learned to use (?:chunk of text)? in regex.
Test data was achieved without bigger hazzles, but
to optimize code required a lot of Reddit browsing
and code reading from blogs. I have mentioned the
sources in a doc string.
