Advent of Code

I've optimistically included folders by year. We'll see if I do this again next year or not.

2021

I've always wanted to improve my Prolog, so let's try to use it for AoC! When a solution led me to learn something interesting or useful about Prolog, I'll include it in the list below. Sometimes those examples will have a comment at the beginning of the file explaining the approach and what I learned. A resource I found myself revisiting constantly was Markus Triska's excellent The Power of Prolog page. If you're interested in getting started with Prolog, I'd highly recommend reading it straight through, at least up to and including Section 20 ("Combinatorial Optimization"). It's a very helpful resource.

All solutions written/tested with SWI-Prolog:

yacin@sif /zfs/home/yacin/code/advent/2021/10 master*
¡ swipl --version
SWI-Prolog version 8.4.1 for x86_64-linux

Helpful Concepts

• utils.pl shows how to use DCGs to read input line by line. slurp/2 is the one I used the most. DCG building block taken from stackoverflow.
• Using assertz/1 and counting the predicates or storing intermediate results. The latter is particularly helpful when base cases that result in failure has generated intermediate data that the caller needs.
• Using CLP(FD) for constraint solving.
• A hacky way to map a character to a variable named by the same letter.
• Some examples of using profile/1.
• I haven't used it yet in a solution, but difference lists and queues will likely be needed at some point.

2023

I started this in awk/bash but quickly bailed. Working through the exercises again but this time in Common Lisp. All solutions written/tested with SBCL:

$ sbcl --version
SBCL 2.4.1

You can run all the test cases with the following command while in the 2023 subdirectory:

$ sbcl --noinform --eval '(progn (asdf:test-system :aoc2023) (quit))'
;;; Computing Hangul syllable names
Running test suite AOC2023
 Running test TEST-DAY-01 ..
Evaluation took:
  0.005 seconds of real time
  0.005207 seconds of total run time (0.005044 user, 0.000163 system)
  100.00% CPU
  2,882,096 bytes consed
...
 Running test TEST-DAY-06 ..
Evaluation took:
  0.062 seconds of real time
  0.062750 seconds of total run time (0.061939 user, 0.000811 system)
  101.61% CPU
  0 bytes consed
  
 Did 12 checks.
    Pass: 12 (100%)
    Skip: 0 ( 0%)
    Fail: 0 ( 0%)

2024

Another year in Common Lisp and I think I'll just stick with that. It's been helpful for learning the language. First year I got all 50 stars! I managed to get all solutions to run in less than a second. This only is slightly cheating for day 24, where I solved part 2 by hand. Tests are only for my inputs.

~/code/advent/2024 master* 18s
¡ make time
sbcl --dynamic-space-size 8192 --eval '(progn (asdf:test-system :aoc2024) (quit))' 2>/dev/null | awk '/TEST/ { split($3,testday,"-") } /seconds of real time/ { printf "day %2d: %5dms\n", testday[2], $1*1000; total+=$1*1000 } END { printf "---------------\ntotal: %6dms\n", total }'
day  1:     0ms
day  2:     4ms
day  3:     2ms
day  4:     6ms
day  5:     2ms
day  6:   219ms
day  7:    69ms
day  8:     1ms
day  9:   105ms
day 10:     1ms
day 11:    16ms
day 12:    64ms
day 13:    12ms
day 14:   156ms
day 15:    12ms
day 16:   165ms
day 17:     1ms
day 18:   419ms
day 19:    84ms
day 20:   740ms
day 21:     1ms
day 22:   672ms
day 23:   128ms
day 24:     1ms
day 25:     5ms

---------------
total:   2885ms

Helpful Links

• https://lispcookbook.github.io/cl-cookbook/