this post was submitted on 05 Nov 2025
13 points (93.3% liked)

Advent Of Code

1122 readers
5 users here now

An unofficial home for the advent of code community on programming.dev! Other challenges are also welcome!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

Everybody Codes is another collection of programming puzzles with seasonal events.

EC 2025

AoC 2024

Solution Threads

M T W T F S S
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25

Rules/Guidelines

Relevant Communities

Relevant Links

Credits

Icon base by Lorc under CC BY 3.0 with modifications to add a gradient

console.log('Hello World')

founded 2 years ago
MODERATORS
Ategon@programming.dev
Sigmatics@lemmy.ca
CameronDev@programming.dev
hades@programming.dev
13
๐Ÿฆ† Everybody.Codes 2025 Quest 1 Solutions ๐Ÿฆ† (programming.dev)
submitted 2 weeks ago by hades@programming.dev to c/advent_of_code@programming.dev
17 comments fedilink hide all child comments
 

Quest 1: Whispers in the Shell

  • Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
  • You can send code in code blocks by using three backticks, the code, and then three backticks or use something such as https://topaz.github.io/paste/ if you prefer sending it through a URL

Link to participate: https://everybody.codes/

you are viewing a single comment's thread
view the rest of the comments
[โ€“] ystael@beehaw.org 2 points 1 week ago

It's been too long since I wrote any Lisp, so obviously I should use the one hallowed by decades of tradition, not any of the fancy new ones with sane naming conventions and unified library systems. :D

(ql:quickload :str)

(defun parse-insn (insn)
  (let ((direction (str:s-first insn))
        (magnitude (parse-integer (str:s-rest insn))))
    (* magnitude (cond ((equal direction "L") -1)
                       ((equal direction "R") 1)
                       (t 0)))))

(defun read-inputs-1 (filename)
  (let ((input-lines (uiop:read-file-lines filename)))
    (destructuring-bind (names _ instructions) input-lines
      (list (str:split "," names)
            (mapcar #'parse-insn (str:split "," instructions))))))

(defun apply-insns-1 (names insns)
  (let ((max-pos (- (length names) 1)))
    (labels ((apply-from (insns pos)
               (if (null insns)
                   (nth pos names)
                   (let* ((maybe-next-pos (+ pos (car insns)))
                          (next-pos (max 0 (min max-pos maybe-next-pos))))
                     (apply-from (cdr insns) next-pos)))))
      (apply-from insns 0))))

(defun main-1 (filename)
  (apply #'apply-insns-1 (read-inputs-1 filename)))

(defun apply-insns-2 (names insns)
  (labels ((apply-from (insns pos)
             (if (null insns)
                 (nth pos names)
                 (let ((next-pos (mod (+ pos (car insns)) (length names))))
                   (apply-from (cdr insns) next-pos)))))
    (apply-from insns 0)))

(defun main-2 (filename)
  (apply #'apply-insns-2 (read-inputs-1 filename)))

(defun apply-insns-3 (names insns)
  (let* ((vnames (coerce names 'vector))
         (n (length vnames)))
    (labels ((apply-from (insns)
               (if (null insns)
                   (aref vnames 0)
                   (let* ((tgt (mod (car insns) n))
                          (src-name (aref vnames 0))
                          (tgt-name (aref vnames tgt)))
                     (setf (aref vnames 0) tgt-name)
                     (setf (aref vnames tgt) src-name)
                     (apply-from (cdr insns))))))
      (apply-from insns))))

(defun main-3 (filename)
  (apply #'apply-insns-3 (read-inputs-1 filename)))