import Text.Parsec
import Text.ParserCombinators.Parsec.Number
+type Disk = (Int -> Bool)
+
main :: IO ()
main = do
text <- readFile "advent15.txt"
part1 disks
part2 disks
-part1 :: [[Int]] -> IO ()
+part1 :: [Disk] -> IO ()
part1 disks = print $ head $ filter (canFall disks) [0..]
-part2 :: [[Int]] -> IO ()
-part2 disks = print $ head $ filter (canFall disks2) [0..5000000]
- where disks2 = id $! map (take 5000000) $ disks ++ [drop 7 $ drop 0 $ cycle [0..(11-1)]]
+part2 :: [Disk] -> IO ()
+part2 disks = print $ head $ filter (canFall disks2) [0..]
+ where disks2 = disks ++ [diskify 7 11 0]
-canFall :: [[Int]] -> Int -> Bool
-canFall ds i = all (\d -> (d!!i) == 0) ds
+canFall :: [Disk] -> Int -> Bool
+canFall ds i = all (\d -> (d i)) ds
instructionFile = instructionLine `endBy` newline
<*> (string " has " *> int)
<*> (string " positions; at time=0, it is at position " *> int)
<* (string ".")
- where diskify n size pos0 = drop n $ drop pos0 $ cycle [0..(size-1)]
-parseIfile :: String -> Either ParseError [[Int]]
+diskify :: Int -> Int -> Int -> (Int -> Bool)
+diskify n size pos0 = (\i -> (size + n + pos0 + i) `mod` size == 0)
+
+parseIfile :: String -> Either ParseError [Disk]
parseIfile input = parse instructionFile "(unknown)" input
-parseIline :: String -> Either ParseError [Int]
+parseIline :: String -> Either ParseError Disk
parseIline input = parse instructionLine "(unknown)" input
successfulParse :: Either ParseError [a] -> [a]