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import Data.Char
import Data.List
type Id = Int
type Len = Int
data Block = Data Id Len | Free Len deriving Show
type HDD = [Block]
getDataFree :: HDD -> Id -> [Len] -> HDD
getDataFree acc id (d:[]) =
acc ++ [Data id d]
getDataFree acc id (d:f:r) =
getDataFree (acc ++ [Data id d, Free f]) (id + 1) r
consume :: String -> HDD
consume file =
getDataFree [] 0 $ map digitToInt $ trim file
where trim = dropWhileEnd isSpace . dropWhile isSpace
frag1 :: HDD -> HDD -> HDD -> HDD
frag1 acc dt (Free _:rest) =
frag1 acc dt rest
frag1 acc (Data di dl:dr) p@(Data pi pl:_)
| di == pi = (Data pi pl:acc)
| otherwise = frag1 (Data di dl:acc) dr p
frag1 acc (Free f:rest) (Data id d:pack)
| d < f = frag1 (Data id d:acc) (Free (f - d):rest) pack
| d == f = frag1 (Data id d:acc) rest pack
| d > f = frag1 (Data id f:acc) rest (Data id (d - f):pack)
frag :: HDD -> HDD
frag hdd = reverse $ frag1 [] hdd (reverse hdd)
checksum :: Int -> Int -> HDD -> Int
checksum acc _ [] = acc
checksum acc ix (Data id len:rest) =
checksum (acc + (sum $ map (id*) [ix..ix+len-1])) (ix + len) rest
part1 :: HDD -> Int
part1 = (checksum 0 0) . frag
main = do
file <- readFile "day09.input"
let hdd = consume file
putStrLn ("Part 1: " ++ (show $ part1 hdd))
--putStrLn ("Part 2: " ++ (show $ part2 hdd))
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