15 lines
559 B
Haskell
15 lines
559 B
Haskell
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module Day1B where
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import Day1A (read')
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import qualified Data.IntSet as S
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handle :: Int -> S.IntSet -> [Int] -> Int
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handle freq history (nextDelta:xs)
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| S.member freq history = freq -- When the frequency is in the history set, return it
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| otherwise = handle (freq + nextDelta) (S.insert freq history) xs -- Recurse otherwise
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handle _ _ _ = error "xs should not be empty :("
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main :: IO ()
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main = interact $ show . handle 0 S.empty . deltaFreqs
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where deltaFreqs = cycle . map read' . lines -- Convert input to Ints and repeat infinitely
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