58 lines
1.7 KiB
Haskell
58 lines
1.7 KiB
Haskell
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{-# LANGUAGE TupleSections #-}
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module Day4 where
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import System.IO
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import ParseLib.Abstract
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import Data.Char (isSpace)
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import Prelude hiding ((*>), (<$), (<*))
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import qualified Data.Map as M
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import Debug.Trace
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main :: IO ()
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main = do
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handle <- openFile "app/Day4-input.txt" ReadMode
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input <- hGetContents handle
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let cards = map (fst . head . parse parseCard) (lines input)
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putStr "Part 1: "
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print $ sum (map score cards)
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putStr "Part 2: "
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print $ sum
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$ foldl
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-- For every card, get the score and get a list of the clones it
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-- would produce and update the accumulator a with a[i] copies.
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(\a c@(Card i _ _) -> update' (a M.! i) a [i+1..i+score' c])
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-- A map of (i, n) where i is the card id and n is the number of copies
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(M.fromList $ map (, 1) [1..length cards])
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cards
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type Id = Int
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type Winning = [Int]
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type Pulls = [Int]
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data Card = Card Id Winning Pulls deriving Show
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whitespace :: Parser Char [Char]
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whitespace = greedy (satisfy isSpace)
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number :: Parser Char Int
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number = whitespace *> natural
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-- Cars needs Int -> [Int] -> [Int] so
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-- number :: Parser Char Int
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-- greedy number :: Parser Char [Int]
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parseCard :: Parser Char Card
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parseCard = Card <$ token "Card" <*> number <* symbol ':' <*>
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greedy number <* whitespace <* symbol '|' <*> greedy number
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intersect :: (Foldable t, Eq a) => t a -> [a] -> [a]
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intersect xs = filter (`elem` xs)
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score :: Card -> Int
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score c = round $ 2 ^^ (score' c - 1)
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score' :: Card -> Int
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score' (Card i w p) = length $ w `intersect` p
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update' :: Int -> M.Map Int Int -> [Int] -> M.Map Int Int
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update' n = foldr (M.update (\x -> Just (x+n)))
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