src/advent08/advent08.hs

   1 {-# LANGUAGE OverloadedStrings #-}
   2
   3 -- import Data.List
   4
   5 import Data.Text (Text)
   6 import qualified Data.Text.IO as TIO
   7
   8 import Data.Void (Void)
   9
  10 import Text.Megaparsec
  11 import Text.Megaparsec.Char
  12 import qualified Text.Megaparsec.Char.Lexer as L
  13 import qualified Control.Applicative as CA
  14
  15
  16 data Tree = Node [Tree] [Int] deriving (Eq, Show)
  17
  18 -- instance Foldable Tree where
  19 --     foldMap f (Node (t: ts) m) = f m <> foldMap (foldMap f) ts
  20
  21 main :: IO ()
  22 main = do
  23         text <- TIO.readFile "data/advent08.txt"
  24         let treeSpec = successfulParse text
  25         let (tree, _) = parseTree treeSpec
  26         -- print $ foldMap sum tree
  27         print $ part1 tree
  28         print $ part2 tree
  29
  30 part1 = sum . metadataOfTree
  31
  32 part2 = valueOfTree
  33
  34
  35 parseTree (c:m:spec) = (Node children metadata, remainder')
  36     where (children, remainder) = parseManyTree c spec
  37           metadata = take m remainder
  38           remainder' = drop m remainder
  39
  40 parseManyTree n spec
  41     | n == 0 = ([], spec)
  42     | otherwise = ((tree:otherTrees), remainder')
  43     where (tree, remainder) = parseTree spec
  44           (otherTrees, remainder') = parseManyTree (n-1) remainder
  45
  46 metadataOfTree (Node trees metadata) = metadata ++ (concatMap metadataOfTree trees)
  47
  48 valueOfTree (Node trees metadata)
  49     | null trees = sum metadata
  50     | otherwise = sum selectedValues
  51     where childValues = map valueOfTree trees
  52           selectedValues = map (\v -> childValues!!(v-1)) $ filter (<= (length trees)) metadata
  53
  54
  55 -- Parse the input file
  56
  57 type Parser = Parsec Void Text
  58
  59 sc :: Parser ()
  60 sc = L.space (skipSome spaceChar) CA.empty CA.empty
  61 -- sc = L.space (skipSome (char ' ')) CA.empty CA.empty
  62
  63 lexeme  = L.lexeme sc
  64 integer = lexeme L.decimal
  65
  66 treeFileP = many integer
  67
  68 successfulParse :: Text -> [Int]
  69 successfulParse input =
  70         case parse treeFileP "input" input of
  71                 Left  _error -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
  72                 Right treeSpec -> treeSpec