2023-12 part 2 in haskell
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2023/12-Hot_Springs/second.hs
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2023/12-Hot_Springs/second.hs
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-- requires cabal install --lib megaparsec parser-combinators MemoTrie
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{-# LANGUAGE DeriveGeneric, TypeOperators, TypeFamilies #-}
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module Main (main) where
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import Control.Applicative.Permutations
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import Control.Monad (void, when)
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import Data.Char qualified as C
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import Data.Either
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import Data.Functor
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import Data.List qualified as L
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import Data.Map qualified as M
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import Data.Maybe
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import Data.MemoTrie
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import Data.Set qualified as S
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import Data.Vector qualified as V
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import Data.Void (Void)
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import GHC.Generics (Generic)
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import Text.Megaparsec
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import Text.Megaparsec.Char
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import Debug.Trace
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exampleExpectedOutput = 525152
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data Tile = Broken | Operational | Unknown deriving (Eq, Generic, Ord)
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instance HasTrie Tile where
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newtype (Tile :->: b) = TileTrie { unTileTrie :: Reg Tile :->: b }
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trie = trieGeneric TileTrie
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untrie = untrieGeneric unTileTrie
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enumerate = enumerateGeneric unTileTrie
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instance Show Tile where
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show Broken = "#"
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show Operational = "."
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show Unknown = "?"
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data Row = Row [Tile] [Int] deriving Show
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type Input = [Row]
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type Parser = Parsec Void String
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parseNumber :: Parser Int
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parseNumber = read <$> some digitChar <* optional (char ',')
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parseTile :: Parser Tile
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parseTile = char '#' $> Broken
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<|> char '.' $> Operational
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<|> char '?' $> Unknown
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parseRow :: Parser Row
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parseRow = Row <$> some parseTile <* space
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<*> some parseNumber <* eol
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parseInput' :: Parser Input
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parseInput' = some parseRow <* eof
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parseInput :: String -> IO Input
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parseInput filename = do
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input <- readFile filename
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case runParser parseInput' filename input of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> return input'
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--type Memo = M.Map [Tile] Int
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--
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--permutations :: Memo -> [Int] -> [Tile] -> (Memo, Int)
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--permutations m [] ts | Broken `L.notElem` ts = (m, 1)
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-- | otherwise = (m, 0)
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--permutations m rr@(r:rs) ts | isJust cached = (m, fromJust cached)
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-- | (length rr - 1) + sum rr < length ts' = (m, 0)
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-- | Operational `L.elem` take r ts' = (m'', operational)
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-- | null ts'' = (m'', operational + 1)
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-- | head ts'' == Broken = (m'', operational)
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-- | otherwise = (m'''', operational + broken)
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-- where
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-- cached = M.lookup ts m
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-- ts' = L.dropWhile (== Operational) ts
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-- ts'' = drop r ts'
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-- (m', operational) = permutations m rr ts'
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-- m'' = if length ts == 5 then M.insert ts operational m' else m'
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-- (m''', broken) = permutations m' rs $ tail ts''
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-- m'''' = if length ts == 5 then M.insert ts broken m''' else m'''
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--
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-- permutations rs (Operational:xs) = map (Operational:) $ permutations rs xs
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-- permutations [r] (Broken:xs) = map (\n -> Broken:Operational:n) $ permutations rs xs
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-- permutations (r:rs) (Broken:xs) = map (replicate l' Broken ++) (if null xs || head xs == Operational then permutations rs xs' else [])
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-- where
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-- l = length (L.takeWhile (/= Operational) xs)
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-- l' = min l (r-1)
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-- xs' = drop l' xs
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-- permutations rr@(r:rs) (Unknown:xs) = (if possible rs xs then map (Operational:) (permutations rr (Operational:xs)) else [])
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-- ++ (if l' == l && possible rs xs' then map (replicate l' Broken ++) (permutations rs xs') else [])
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-- where
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-- l = length (L.takeWhile (/= Operational) xs)
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-- l' = min l (r-1)
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-- xs' = drop l' xs
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-- permutations _ _ = []
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permutations = memo2 permutations'
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where
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permutations' :: [Int] -> [Tile] -> Int
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permutations' [] ts | Broken `L.notElem` ts = 1
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| otherwise = 0
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permutations' _ [] = 0
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permutations' rs (Operational:ts) = permutations rs ts
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permutations' (r:rs) (Broken:ts) = case splitAt (r-1) ts of
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(a, t:b) | length a == r-1, Operational `L.notElem` a, t /= Broken -> permutations rs b
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(a, []) | length a == r-1, Operational `L.notElem` a -> permutations rs []
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_ -> 0
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permutations' rs (Unknown:ts) = permutations rs (Operational:ts) + permutations rs (Broken:ts)
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compute :: Input -> Int
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compute input = sum $ map compute' expand
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where
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compute' :: Row -> Int
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compute' (Row tiles record) = permutations record tiles
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expand = map expandOne input
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expandOne (Row tiles record) = Row (L.intercalate [Unknown] $ replicate 5 tiles) (concat $ replicate 5 record)
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main :: IO ()
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main = do
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example <- parseInput "example"
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let exampleOutput = compute example
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when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
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input <- parseInput "input"
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print $ compute input
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