day7

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

day7'.hs

@@ -0,0 +1,57 @@
+import Data.Tree
+
+main :: IO ()
+main = do
+  tree <- flip parse (emptyFs "/") . map words . lines <$> readFile "day7.in"
+  putStr "Q1: "
+  print $
+    foldTree
+      ( \x xs ->
+          if null xs || snd x > 100000 then sum xs else snd x + sum xs
+      )
+      tree
+  putStr "Q2: "
+  let maxStorage = 70000000
+  let spaceNeeded = 30000000 - (maxStorage - snd (rootLabel tree))
+  print $
+    foldTree
+      ( \x xs ->
+          if snd x < spaceNeeded
+            then minimum (maxStorage : xs)
+            else minimum (snd x : xs)
+      )
+      tree
+
+tail' :: [a] -> [a]
+tail' = drop 1
+
+emptyFs :: String -> Tree (String, Int)
+emptyFs n = Node (n, 0) []
+
+insertFs :: Tree (String, Int) -> String -> Tree (String, Int) -> Tree (String, Int)
+insertFs (Node n xs) name dir = Node (fst n, snd n + snd (rootLabel dir)) (dir : xs)
+
+totalSize :: [Tree (String, Int)] -> Int
+totalSize = sum . map (snd . rootLabel)
+
+ls :: [[String]] -> [Tree (String, Int)]
+ls = map (\[a, b] -> Node (b, read a) []) . filter ((/= "dir") . head)
+
+parse :: [[String]] -> Tree (String, Int) -> Tree (String, Int)
+parse input fs = snd $ parse' input fs
+
+parse' :: [[String]] -> Tree (String, Int) -> ([[String]], Tree (String, Int))
+parse' input fs
+  | null input || cur !! 1 == "cd" && cur !! 2 == ".." = (tail' input, fs)
+  | cur !! 1 == "ls" =
+    let (children, rest) = span ((/= "$") . head) (tail' input)
+        childFs = ls children
+        name = fst $ rootLabel fs
+     in parse' rest (Node (name, totalSize childFs) childFs)
+  | otherwise =
+    let name = cur !! 2
+        (nextInput, newFs) = parse' (tail' input) (emptyFs name)
+        replaced = insertFs fs name newFs -- replace empty directory
+     in parse' nextInput replaced
+  where
+    cur = head input

day7.hs

@@ -0,0 +1,65 @@
+import Data.Tree
+
+-- this solution assumes that empty directories can exist,
+-- if you want to ignore that, there is a slightly more compact code as day7'.hs
+-- needs cleaning and improvement
+
+main :: IO ()
+main = do
+  tree <- flip parse (emptyFs "/") . map words . lines <$> readFile "day7.in"
+  putStr "Q1: "
+  print $
+    foldTree
+      ( \x xs ->
+          if null xs || snd x > 100000 then sum xs else snd x + sum xs
+      )
+      tree
+  putStr "Q2: "
+  let maxStorage = 70000000
+  let spaceNeeded = 30000000 - (maxStorage - snd (rootLabel tree))
+  print $
+    foldTree
+      ( \x xs ->
+          if snd x < spaceNeeded
+            then minimum (maxStorage : xs)
+            else minimum (snd x : xs)
+      )
+      tree
+
+tail' :: [a] -> [a]
+tail' = drop 1
+
+emptyFs :: String -> Tree (String, Int)
+emptyFs n = Node (n, 0) []
+
+replaceFs :: Tree (String, Int) -> String -> Tree (String, Int) -> Tree (String, Int)
+replaceFs (Node n xs) name fs =
+  let (h, t) = span ((/= name) . fst . rootLabel) xs
+   in Node
+        (fst n, snd n + snd (rootLabel fs))
+        (h ++ [fs] ++ tail' t)
+
+totalSize :: [Tree (String, Int)] -> Int
+totalSize = sum . map (snd . rootLabel)
+
+ls :: [[String]] -> [Tree (String, Int)]
+ls = map (\[a, b] -> if a == "dir" then Node (b, 0) [] else Node (b, read a) [])
+
+parse :: [[String]] -> Tree (String, Int) -> Tree (String, Int)
+parse input fs = snd $ parse' input fs
+
+parse' :: [[String]] -> Tree (String, Int) -> ([[String]], Tree (String, Int))
+parse' input fs
+  | null input || cur !! 1 == "cd" && cur !! 2 == ".." = (tail' input, fs)
+  | cur !! 1 == "ls" =
+    let (children, rest) = span ((/= "$") . head) (tail' input)
+        childFs = ls children
+        name = fst $ rootLabel fs
+     in parse' rest (Node (name, totalSize childFs) childFs)
+  | otherwise =
+    let name = cur !! 2
+        (nextInput, newFs) = parse' (tail' input) (emptyFs name)
+        replaced = replaceFs fs name newFs -- replace empty directory
+     in parse' nextInput replaced
+  where
+    cur = head input