Advent Of Code

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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

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🐒 - 2024 DAY 22 SOLUTIONS - 🐒 (programming.dev)

submitted 3 days ago by [email protected] to c/[email protected]

17 comments fedilink hide all child comments

Day 22: Monkey Market

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[–] [email protected] 2 points 3 days ago

Haskell

solution

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