72 lines
2.1 KiB
Haskell
72 lines
2.1 KiB
Haskell
import Data.Tree
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-- this solution assumes that empty directories can exist,
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-- if you want to ignore that, there is a slightly different code in day7'.hs
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-- needs cleaning and improvement
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main :: IO ()
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main = do
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tree <- snd . flip parse (emptyFs "/") . map words . lines <$> readFile "day7.in"
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putStr "Q1: "
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print $
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foldTree
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( \x xs ->
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if null xs || snd x > 100000 then sum xs else snd x + sum xs
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)
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tree
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putStr "Q2: "
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let maxStorage = 70000000
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let spaceNeeded = 30000000 - (maxStorage - snd (rootLabel tree))
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print $
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foldTree
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( \x xs ->
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if snd x < spaceNeeded
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then minimum (maxStorage : xs)
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else minimum (snd x : xs)
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)
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tree
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type Filesystem = Tree (String, Int)
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tail' :: [a] -> [a]
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tail' = drop 1
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-- wrapper to create an empty tree
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emptyFs :: String -> Filesystem
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emptyFs n = Node (n, 0) []
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-- This function is to replace a filesystem by name
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-- Used to replace empty directories with parsed directories in code
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replaceFs :: Filesystem -> String -> Filesystem -> Filesystem
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replaceFs (Node n xs) name fs =
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let (h, t) = span ((/= name) . fst . rootLabel) xs
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in Node
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(fst n, snd n + snd (rootLabel fs))
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(h ++ [fs] ++ tail' t)
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-- Sum of all filesystems in the list
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-- Used to calculate sum of leaves in code
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totalSize :: [Filesystem] -> Int
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totalSize = sum . map (snd . rootLabel)
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-- All directories/files are parsed here into leaves
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ls :: [[String]] -> [Filesystem]
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ls = map (\[a, b] -> if a == "dir" then Node (b, 0) [] else Node (b, read a) [])
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-- main function where stuff happens
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parse :: [[String]] -> Filesystem -> ([[String]], Filesystem)
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parse input fs
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| null input || cur == ["$", "cd", ".."] = (tail' input, fs)
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| cur == ["$", "ls"] =
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let (children, rest) = span ((/= "$") . head) (tail' input)
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leaves = ls children
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name = fst $ rootLabel fs
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in parse rest (Node (name, totalSize leaves) leaves)
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| otherwise =
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let name = cur !! 2
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(nextInput, newFs) = parse (tail' input) (emptyFs name)
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replaced = replaceFs fs name newFs -- replace empty directory
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in parse nextInput replaced
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where
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cur = head input
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