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advent-2020-clojure

This is my code for the 2020 Advent of Code, all solutions in Clojure.

All code is under the src directory. Each solution-file is named dayNN.clj and contains both puzzle solutions for that day. These are the publically-facing functions part-1 and part-2. These files are the code exactly as I used it to solve and submit the answers. If I revisit any of the days and try to clean up or optimize the solutions, that work will be in a separate file that will be named dayNNbis.clj. (Except that I will likely go back and comment the code after the fact, when I'm not racing the clock.)

The resources directory contains the input data for each day. These files are named for the day (dayNN.txt), and files with the example input are named dayNN-example.txt.

The test directory contains unit tests. I'm experimenting with these for the first time this go-around, so I'll say more here once I have a better feel.

Stats

Number of answers correct on first submission: 45/50 (90%)

Highest finish for first half: 1662 (day 19)

Highest finish for second half: 793 (day 19)

Usage

This project is managed with Leiningen. Running the following will download any dependencies and start a REPL:

lein repl

Postmortem

Advent of Code 2020 is now completed. Overall, I did well. I placed 3rd on both leaderboards that I'm on (NVIDIA and Clojure), and only had one day (day 20) that exceeded 24 hours' time in getting both solutions. I did a little worse in terms of submitting wrong answers; last year I only submitted a wrong answer twice, for an average of 96%. This year I had five wrong submissions for an average of 90%.

It is very likely that I won't be able to participate in AoC next year (2021) or the year after (2022). I'm starting a MS program in Computer Science next month and expect Decembers to be when final exams land. But I will be following the #adventofcode channel on the Clojure slack, as this year it was much more active than I remember last year being. I had some great interaction with other Clojure programmers this time around.

Links

I'd like to link to three other Clojure repos in particular:

I learned a great deal from several of the coders I talked to on slack, but these three especially. Zelark's code is particularly concise and clean.

Lessons and Take-Aways

My take-aways from this year (for when I can return to AoC) are:

  1. I need better templates to work with. I told myself this last year but never got around to it. I used Mitchell Hanburg's starter as a basis for my own, but I can see a lot of areas in which I can put my own spin on it to better suit my style:
    1. Either extend the unit-test elements or drop them. They didn't prove useful and the command to run each (lein test path/to/file.clj) was just too much typing when in a hurry. It was faster to just have the example input loaded into a def in the REPL.
    2. More abstractions for input parsing, based on past experiences. This is also linked to the next (top-level) point, but I did spent too much time each day repeating stuff that could/should have been in the templates I was using.
    3. Make the advent-clojure-basis repository work as a template, so that I can start off new years with less up-front tweaking.
  2. Desperately need some utils-code written, in particular around the reading/parsing of the input data.
    1. The starter that I based mine on covers this partially, in that it places all the input data files under the resources directory and reads them as such. Then it provides a -main fn that handles calling a given day/part, feeding it the input already read in via slurp.
    2. To this I should add common cases, including: breaking into lines, breaking into blocks (using \n\n as a split-separator), lines of integers, etc.
    3. One useful pattern I adopted from someone else, was to have a generic parse-input that takes both the input and a fn, splits the input into lines and feeds them to the given function. Might be a way to extend this even more with comp, maybe?
    4. Get some basic stuff in as well, such as:
      1. Defining/manipulating coordinate systems (2D, hexagonal)
      2. Basic searching (A*, etc.)
      3. ASCII-art-based operations (parsing, rotation, etc.)
  3. Lastly, I need to use Clojure more during the year.
    1. I spent far too much time looking up basic functions for their arguments' type and/or order.
    2. I made certain mistakes too often (like (cons list value) instead of (cons value list)).
    3. There are still a lot of Clojure keywords I don't even know because I haven't used them before (not to mention the ones that I don't even know that I don't know).

Credits

This is based on my Advent of Code Clojure Basis repository, which itself is based almost entirely on Mitchell Hanburg's Advent of Code Clojure Starter.

License

Copyright © 2020 Randy J. Ray

Distributed under the Eclipse Public License either version 2.0 or (at your option) any later version.