Day 4 Notes

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| Part 1 |
+--------+

$ elixir day4part1.exs
210

Thoughts:

Parse each passport into a list of key-value pairs, and extract the keys.
Not sure if there will be extra keys, so store required keys in a Mapset, which means I can use
MapSet.subset to make sure all the required keys are present.
Embedded enums are kind of ugly.
Nice usage of Enum.into, IMO 🍠.

+--------+
| Part 2 |
+--------+

$ elixir day4part2.exs
131

Thoughts:

Need the values too now, so refactor a bit to preserve them, storing each passport at a map.
Can still use part 1 logic to filter out passports that have missing keys.
 - just pull out the keys and convert to a MapSet as before.
Delete the cid key if present, since needs to be ignored.

Validation code:
Mostly just implementing the spec.
Use regex for fiddly requirements.
hgt was a bit annoying, really wanted to fail-fast if the regex failed to match the units,
maybe will come back to that and think of a nicer way later.
For valid?: Is there a nicer way to call a bunch of functions with the same argument and
aggregate their results? 🤔


+------------------+
| Overall Thoughts |
+------------------+

Starting to take me longer now, about an hour for this one.
Ended up not using Enum.reduce here, but every time I do use it I forget the order of the
acc/item pair in the reducer function... 😩