Day 08.

app/Main.hs

@@ -30,4 +30,4 @@ import qualified Day24
 import qualified Day25
 
 main :: IO ()
-main = Day07.main
+main = Day08.main

src/Day08.hs

@@ -1,6 +1,25 @@
 module Day08 (main) where
 
+import Data.Tree (Tree(Node), rootLabel, subForest)
+
+type Metadata = [Int]
+
+parseTree :: ([Tree Metadata], [Int]) -> ([Tree Metadata], [Int])
+parseTree (nodes, (c:m:input)) =
+    let (children, remaining) = iterate parseTree ([], input) !! c
+    in  (Node (take m remaining) (reverse children) : nodes, drop m remaining)
+
+part1 :: Tree Metadata -> Int
+part1 = sum . fmap sum
+
+part2 :: Tree Metadata -> Int
+part2 tree =
+    if   null (subForest tree) then sum (rootLabel tree)
+    else sum . map (part2 . (subForest tree !!) . subtract 1) . filter (<= length (subForest tree)) $ rootLabel tree
+
 main :: IO ()
 main = do
-    input <- readFile "input/08.txt"
-    print input
+    input <- map read . words <$> readFile "input/08.txt"
+    let tree = head . fst $ parseTree ([], input)
+    print $ part1 tree
+    print $ part2 tree