38 lines
1.3 KiB
Haskell
38 lines
1.3 KiB
Haskell
import Lib (split)
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main :: IO ()
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main = do
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input <- readFile "day5.in"
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let [crates, cmds] = split "" $ lines input
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let cratesList = init $ parseCrates $ init crates
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let cmdsList = parseCmds cmds
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putStr "Q1: "
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print $ q1 cratesList cmdsList
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putStr "Q2: "
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print $ q2 cratesList cmdsList
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q1 :: [[Char]] -> [(Int, Int, Int)] -> [Char]
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q1 crates cmds = map head $ foldl (\x xs -> moveCrates x xs True) crates cmds
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q2 :: [[Char]] -> [(Int, Int, Int)] -> [Char]
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q2 crates cmds = map head $ foldl (\x xs -> moveCrates x xs False) crates cmds
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-- Computers are fast, really, not optimising right now
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moveCrates :: [[Char]] -> (Int, Int, Int) -> Bool -> [[Char]]
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moveCrates crates (n, a, b) rev =
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let (head, tail) = splitAt n $ crates !! a
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in replace b (replace a crates tail) ((if rev then reverse head else head) ++ crates !! b)
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where
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replace :: Int -> [a] -> a -> [a]
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replace i xs x = take i xs ++ [x] ++ drop (i + 1) xs
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parseCrates :: [[Char]] -> [[Char]]
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parseCrates ([] : _) = [[]]
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parseCrates crates = parseCrate crates : parseCrates (map (drop 4) crates)
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where
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parseCrate :: [[Char]] -> [Char]
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parseCrate = foldr (\(_ : x : _ : _) xs -> if x /= ' ' then x : xs else xs) []
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parseCmds :: [[Char]] -> [(Int, Int, Int)]
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parseCmds = foldr (\x xs -> let y = split ' ' x in (read $ y !! 1, read (y !! 3) - 1, read (y !! 5) - 1) : xs) []
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