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

Advent Of Code

3 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