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[hs] Clean up 2020_13

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Joscha 2020-12-13 11:45:00 +00:00
parent 05fef92fee
commit dde5269d39
1 changed files with 8 additions and 5 deletions
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13
hs/src/Aoc/Y2020/D13.hs
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@ -27,16 +27,19 @@ data Bus = Bus
, bDelta :: Integer
} deriving (Show)
departsAt :: Bus -> Integer -> Bool
departsAt bus time = (time + bDelta bus) `mod` bId bus == 0
includeBus :: Bus -> (Integer, Integer) -> (Integer, Integer)
includeBus bus (time, step) =
let time' = fromJust $ find (\t -> (t + bDelta bus) `mod` bId bus == 0) $ iterate (+ step) time
let time' = fromJust $ find (bus `departsAt`) $ iterate (+ step) time
step' = step * bId bus
in (time', step')
earliestTimestamp :: [Maybe Integer] -> Integer -> Integer
earliestTimestamp buses start =
earliestTimestamp :: [Maybe Integer] -> Integer
earliestTimestamp buses =
let busDeltas = sortOn (Down . bId) [Bus bus delta | (Just bus, delta) <- zip buses [0..]]
in fst $ foldl' (flip includeBus) (start, 1) busDeltas
in fst $ foldl' (flip includeBus) (0, 1) busDeltas
solver :: (Integer, [Maybe Integer]) -> IO ()
solver (earliest, buses) = do
@ -47,7 +50,7 @@ solver (earliest, buses) = do
putStrLn ""
putStrLn ">> Part 2"
print $ earliestTimestamp buses 100_000_000_000_000
print $ earliestTimestamp buses
day :: Day
day = dayParse parser solver