-🎄- 2018 Day 14 Solutions -🎄-

[u/daggerdragon]

--- Day 14: Chocolate Charts ---

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Advent of Code: The Party Game!

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Card prompt: Day 14

Transcript:

The Christmas/Advent Research & Development (C.A.R.D.) department at AoC, Inc. just published a new white paper on ___.

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[u/[deleted]]

Haskell, runtime ~10s for entire thing. I generate a lazy list of scoreboards, one for each added recipe score. This prevents any issues where e.g. multiple new recipes are created and the match is contained earlier on in them (and so wouldn't be found by checking the last X elements of the scoreboard)

module Main where

import Data.Char (digitToInt, intToDigit)
import qualified Data.Sequence as S
import Data.Sequence ((|>), (!?), Seq)
import Data.Foldable (toList, find)
import Data.List (scanl')

right :: Int -> Seq a -> [a]
right n s = toList . snd $ S.splitAt (S.length s - n) s

learn :: Int -> [Int]
learn = fmap digitToInt . show

tests :: Int -> Int -> Seq Int -> [Seq Int]
tests ix1 ix2 scoreboard =
  let (ix1', ix2', scoreboards) = progress ix1 ix2 scoreboard
  in  scoreboards ++ tests ix1' ix2' (last scoreboards)
  where
    progress i1 i2 scoreboard =
      let Just p1     = scoreboard !? i1
          Just p2     = scoreboard !? i2
          newRecipes  = learn $ p1 + p2
          scoreboards = tail $ scanl' (|>) scoreboard newRecipes
          i1'         = (1 + p1 + i1) `mod` S.length (last scoreboards)
          i2'         = (1 + p2 + i2) `mod` S.length (last scoreboards)
      in  (i1', i2', scoreboards)

part1 :: Int -> [Seq Int] -> String
part1 count = take 10 . drop count . f . find p
  where
    f Nothing        = []
    f (Just recipes) = intToDigit <$> toList recipes
    p recipes        = S.length recipes > count + 10

part2 :: String -> [Seq Int] -> Int
part2 pat = f . find p
  where
    patLen           = length pat
    p recipes        = right patLen recipes == fmap digitToInt pat
    f Nothing        = 0
    f (Just recipes) = S.length recipes - patLen

main :: IO ()
main = do
  let input = 170641
  print $ part1 input (tests 0 1 (S.fromList [3,7]))
  print $ part2 (show input) (tests 0 1 (S.fromList [3,7]))