AoCDay8Part1.hs

module AoCDay8Part1 where
  
data Node = Node [Node] [Int]

solve :: [Int] -> ([Int], Node)
solve (nChild:nEntries:rest) =
  (remainingToBeParsed, Node children entries)
  where
    remainingToBeParsed      = drop nEntries restChildren
    entries                  = take nEntries restChildren
    (restChildren, children) = makeChildren nChild (rest, [])

makeChildren :: Int -> ([Int], [Node]) -> ([Int], [Node])
makeChildren n (remaining, children)
  | n == length children    = (remaining, children)
  | otherwise               = makeChildren n (next, nextChild:children)
  where (next, nextChild)   = solve remaining

sumEntries :: Node -> Int
sumEntries (Node children entries)
  | length children == 0    = sum entries
  | otherwise               = sum (entries <> map sumEntries children)

testInput = "2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2"

main :: IO ()
main = 
  print $ sumEntries $ snd $ solve $ read <$> words testInput