Advent Of Code

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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 2025

Solution Threads

M	T	W	T	F	S	S
1	2	3	4	5	6	7
8	9	10	11	12

Visualisations Megathread

Rules/Guidelines

• Follow the programming.dev instance rules
• Keep all content related to advent of code in some way
• If what youre posting relates to a day, put in brackets the year and then day number in front of the post title (e.g. [2024 Day 10])
• When an event is running, keep solutions in the solution megathread to avoid the community getting spammed with posts

Relevant Communities

• !programming@programming.dev
• !challenges@programming.dev

Relevant Links

• Advent of Code Homepage

Credits

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

console.log('Hello World')

MODERATORS

import Data.List  

readInput = map readMove . lines  
  where  
    readMove (d : ds) =  
      let n = read ds :: Int  
       in case d of  
            'L' -> -n  
            'R' -> n  

part1 = length . filter ((== 0) . (`mod` 100)) . scanl' (+) 50  

part2 = fst . foldl' count (0, 50)  
  where  
    count (z, p) d =  
      let (q, r) = (p + d) `divMod` 100  
          a = if p == 0 && d < 0 then -1 else 0  
          b = if r == 0 && d < 0 then 1 else 0  
       in (z + abs q + a + b, r)  

main = do  
  input <- readInput <$> readFile "input01"  
  print $ part1 input  
  print $ part2 input