AoC/2022/day07/day07.hs

import Data.List

type Name = String
type Size = Int

data Inode = File Name Size | Folder Name [Inode] deriving Show
data ICrumb = ICrumb Name [Inode] deriving Show

type IZipper = (Inode, [ICrumb])

main :: IO ()
main = do
  input <- map words <$> lines <$> readFile "input"
  let fullFS = walk (tail input) ((Folder "/" []), [])
  let sizeList = getDirSizeList $ upTop fullFS
  print $ sum $ filter (<100000) sizeList
  let toDelete = (subtract 40000000) $ getDirSize $ upTop fullFS
  print $ head $ dropWhile (< toDelete) $ sort sizeList


up :: IZipper -> IZipper
up (node, ICrumb name nodes:crumbs) = (Folder name (node:nodes), crumbs)

upTop :: IZipper -> IZipper
upTop (inode, []) = (inode, [])
upTop z = upTop (up z)

newFile :: Inode -> IZipper -> IZipper
newFile node (Folder name nodes, crumbs) = (Folder name (node:nodes), crumbs)

goTo :: Name -> IZipper -> IZipper
goTo name (Folder fname nodes, crumbs) =
     let (ls, node:rs) = break (nameIs name) nodes
     in (node, ICrumb fname (ls++rs):crumbs)


nameIs :: Name -> Inode -> Bool
nameIs name (Folder folderName _) = name == folderName
nameIs name (File fileName _) = name == fileName

walk :: [[String]] -> IZipper -> IZipper
walk (("$":"cd":name:[]):xs) z = walk xs $ if name==".." then up z else goTo name z
walk (("$":"ls":[]):xs) z = walk xs z
walk (("dir":name:[]):xs) z = walk xs $ newFile (Folder name []) z
walk ((size:name:[]):xs) z = walk xs $ newFile (File name (read size)) z
walk _ z = z


getDirSize :: IZipper -> Int
getDirSize ((Folder _ nodes),_) = sum $ map getSize nodes
    where getSize (File _ size) = size
          getSize folder = getDirSize (folder,[])
getDirSize _ = 0

getDirSizeList :: IZipper -> [Int]
getDirSizeList ((Folder _ nodes),_) = getDirSize ((Folder "" nodes),[]) : concat [getDirSizeList (node,[]) | node<-nodes]
getDirSizeList _ = []