Advent of Code, 2021

These are my advent of code solutions. In the same way as last year, I do every day in a different language.

1. Must do all days in different languages, except those days which continue from other days' solutions (e.g. IntCode computer, 2019)
2. If I do a day in multiple different languages, I can "pick" the language for that day, as long as the resulting picks adhere to rule 1.
3. If I wish to use a language that I have already used, I can go back and redo the day that language was previously used for (in a different language), thus freeing it up for the new day.
4. Languages cannot be too similar, keeping in spirit of the rules (e.g. bash/zsh, typescript/javascript, haskell/purescript [controversial, I know])
5. I may write preprocessors to transform the input into something palatable to the language, but generally this is discouraged.

Languages and solutions so far can be got by running ./summarize.

                            |1|1|1|1|1|
          |1|2|3|4|5|6|7|8|9|0|1|2|3|4|
awk       | |█| | | | | |█| | | | | | |
brainfuck | | | | | |░| | | | | | | | |
c         | | | | | | | | | | | | |▒|█|
dc        | | | | | |█| | | | | | | | |
haskell   |█|█|█|█| | | | | | | | | |░|
j         |█| |█| | | | | | | | | | | |
jq        |█| | | | | | | | | | | | | |
julia     | | | | | | |█| | | | | | | |
multifuck | | | | | |░| | | | | | | | |
nim       | | | | | | | | | | | | |█| |
nix       |█| | | | | | | | | | | | | |
octave    | | |█|█|█| |█| | | | | | | |
perl      | |█| |█| |█| | | | | | | | |
python    | | | | | | | |█|█| |█| | | |
ruby      | | | | | |█| | | | | |█| | |
rust      | | | |█| | | | | | | | | | |
scala     | | | | | | | | |█| | | | | |
sh        | |█| | | | | | | | | | | | |
zig       | | | | | | | | | |█| | | | |

Light/medium fill means solution 1 only or solution 2 only.