41 lines
985 B
Haskell
41 lines
985 B
Haskell
module Main (main) where
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import Control.Monad.State
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import Data.Traversable
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import Text.Read (readMaybe)
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main :: IO ()
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main = do
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Just input <-
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traverse
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( \case
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'L' : (readMaybe -> Just i) -> Just (L, Inc i)
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'R' : (readMaybe -> Just i) -> Just (R, Inc i)
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_ -> Nothing
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)
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. lines
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<$> readFile "inputs/examples/1"
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print
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. sum
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. flip evalState 50
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$ for input \(d, i) -> state \p ->
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let p' = step i d p
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in (Count if p' == 0 then 1 else 0, p')
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data Direction = L | R
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deriving (Eq, Ord, Show)
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newtype Pos = Pos Int
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deriving newtype (Eq, Ord, Show, Num)
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newtype Inc = Inc Int
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deriving newtype (Eq, Ord, Show, Num)
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newtype Count = Count Int
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deriving newtype (Eq, Ord, Show, Num)
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step :: Inc -> Direction -> Pos -> Pos
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step (Inc i) d (Pos p) = Pos case d of
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L -> (p - i) `mod` 100
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R -> (p + i) `mod` 100
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