Advent of Code 2020 in Awk

Each day's solution solves both parts of the puzzle for that day. The answers are printed on separate lines. Input can be provided to standard in.

For the problem descriptions, and to get your own input, head over to Advent of Code.

awk -f "day_$N/solution.awk" < input

The solutions may not work on every input, even though I tried to keep them reasonably general.

Not feeling like browsing through 25 separate files, with extranious whitespace, longer than one letter names and relatively straight forward code?

Check tldr.awk for short and sweat solutions for all the problems.

Note worthy:

the form factor is "less than 5 lines at 80 columns" to fit within the r/adventofcode Megathread format
the file is not runnable as is, you can copy/paste the relevant section, and run it separately
these may rely on specific, non standard, behaviour (e.g. this fix breaks day 17 formatting)
there is one day (20), with only part 1 solution, otherwise, each solves both parts
the algorithms used may not always be as efficient as the more verbose ones, but not total garbage either

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