Advent Of Code

34 users here now

An unofficial home for the advent of code community on programming.dev!

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.

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

• 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 Control.Arrow
import Data.Bits
import Data.List
import qualified Data.Map as M

parse = fmap (secretNums . read) . lines

secretNums :: Int -> [Int]
secretNums = take 2001 . iterate (step1 >>> step2 >>> step3)
 where
  step1 n = ((n `shiftL` 06) `xor` n) .&. 0xFFFFFF
  step2 n = ((n `shiftR` 05) `xor` n) .&. 0xFFFFFF
  step3 n = ((n `shiftL` 11) `xor` n) .&. 0xFFFFFF

part1 = sum . fmap last
part2 = maximum . M.elems . M.unionsWith (+) . fmap (deltas . fmap (`mod` 10))

deltas l = M.fromListWith (\n p -> p) $ flip zip (drop 4 l) $ zip4 diffs (tail diffs) (drop 2 diffs) (drop 3 diffs)
 where
  diffs = zipWith (-) (tail l) l

main = getContents >>= print . (part1 &&& part2) . parse