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๐Ÿ’ƒ - 2025 DAY 3 SOLUTIONS - ๐Ÿ’ƒ (programming.dev)
submitted 9 months ago by [M] to c/advent_of_code@programming.dev
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Day 3: Lobby

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[โ€“] 4 points 9 months ago (1 child)

Haskell

Yay, dynamic programming!

import Data.Map qualified as Map  

maxJolt :: Int -> [Char] -> Int  
maxJolt r xs = read $ maximize r 0  
  where  
    n = length xs  
    maximize =  
      (curry . (Map.!) . Map.fromList . (zip <*> map (uncurry go)))  
        [(k, o) | k <- [1 .. r], o <- [r - k .. n - k]]  
    go k o =  
      maximum $ do  
        (x, o') <- drop o $ zip xs [1 .. n - (k - 1)]  
        return . (x :) $ if k == 1 then [] else maximize (k - 1) o'  

main = do  
  input <- lines <$> readFile "input03"  
  mapM_ (print . sum . (`map` input) . maxJolt) [2, 12]
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  • [โ€“] 1 point 9 months ago

    Version 2. I realized last night that my initial approach was way more complicated than it needed to be...

    import Data.List
import Data.Semigroup

maxJolt :: Int -> [Char] -> Int
maxJolt r xs = read $ go r (length xs) xs
  where
    go r n xs =
      (\(Arg x xs) -> x : xs) . maximum $
        do
          (n', x : xs') <- zip (reverse [r .. n]) (tails xs)
          return . Arg x $ if r == 1 then [] else go (r - 1) (n' - 1) xs'

main = do
  input <- lines <$> readFile "input03"
  mapM_ (print . sum . (`map` input) . maxJolt) [2, 12]
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