Day 16 Notes

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

$ elixir day16part1.exs
28884

Thoughts:

Slightly complex input to parse this time. Most of the solution is parsing.
The actual logic: Use Enum.any?(rules) to check if a ticket satisfies any of the rules.
Filter those results by only those that are not valid.
Flat map the filtered tickets, to get a flat list of fields.
Sum the result.


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

$ elixir day16part2.exs
1001849322119

Thoughts:

More complicated as I initially thought, because most columns are valid for more than
one rule. Interestingly no column is valid for the *same* number of rules, which makes me
think this is a manifestation of some maths problem I don't know about.

Anyway, solve it by:
* Transposing the tickets into lists of "columns"
* Match each column against the rules it satisfies
* Starting with the column that only matches one rule, mark that column as solved.
* Continue for subsequent rules, removing the solved columns from the set of rules it
  satisfies as we go.

I'm sure there is a more efficient way to handle this rather than the building up n lists
and then for each entry removing that from the remaining lists.

** UPDATE 17 December **

I refactored part 2, and I'm much happier with it now.
Most of the simplifications I thought of myself, but there was one change I read on the ElixirForum,
using Enum.zip to transpose the ticket rows to columns, which I wanted to use, so I committed that
change only to day16paet2-simpler-transpose.exs.


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| Overall Thoughts |
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Spent a bit too long on silly mistakes in this one. Think I need to consider my development
process to help avoid making errors, especially when dealing with multiple related data structures
/ representation of those data structures.

Also, I'm finding these daily puzzles a bit too distracting from work. I think after today
I'm going to relegate them to the weekend. Doing them in the evenings has too much potential
to spill over into the next day.