2020-12-16 09:11:24 +00:00
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Day 16 Notes
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+--------+
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| Part 1 |
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+--------+
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$ elixir day16part1.exs
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28884
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Thoughts:
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2020-12-16 14:57:57 +00:00
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Slightly complex input to parse this time. Most of the solution is parsing.
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The actual logic: Use Enum.any?(rules) to check if a ticket satisfies any of the rules.
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Filter those results by only those that are not valid.
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Flat map the filtered tickets, to get a flat list of fields.
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Sum the result.
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2020-12-16 09:11:24 +00:00
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+--------+
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| Part 2 |
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+--------+
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$ elixir day16part2.exs
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2020-12-16 14:57:57 +00:00
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1001849322119
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2020-12-16 09:11:24 +00:00
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Thoughts:
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2020-12-16 14:57:57 +00:00
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More complicated as I initially thought, because most columns are valid for more than
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one rule. Interestingly no column is valid for the *same* number of rules, which makes me
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think this is a manifestation of some maths problem I don't know about.
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Anyway, solve it by:
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* Transposing the tickets into lists of "columns"
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* Match each column against the rules it satisfies
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* Starting with the column that only matches one rule, mark that column as solved.
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* Continue for subsequent rules, removing the solved columns from the set of rules it
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satisfies as we go.
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I'm sure there is a more efficient way to handle this rather than the building up n lists
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and then for each entry removing that from the remaining lists.
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2020-12-17 03:47:15 +00:00
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** UPDATE 17 December **
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I refactored part 2, and I'm much happier with it now.
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Most of the simplifications I thought of myself, but there was one change I read on the ElixirForum,
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using Enum.zip to transpose the ticket rows to columns, which I wanted to use, so I committed that
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change only to day16paet2-simpler-transpose.exs.
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2020-12-16 09:11:24 +00:00
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+------------------+
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| Overall Thoughts |
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+------------------+
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Spent a bit too long on silly mistakes in this one. Think I need to consider my development
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2020-12-16 14:57:57 +00:00
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process to help avoid making errors, especially when dealing with multiple related data structures
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/ representation of those data structures.
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2020-12-16 09:11:24 +00:00
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Also, I'm finding these daily puzzles a bit too distracting from work. I think after today
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I'm going to relegate them to the weekend. Doing them in the evenings has too much potential
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to spill over into the next day.
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