94 lines
2.7 KiB
Haskell
94 lines
2.7 KiB
Haskell
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import Data.Char (digitToInt)
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main :: IO ()
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main = do
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input <- getContents
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let
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octopodes = (map (map digitToInt) . lines) input
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(putStrLn . show . solution1) octopodes
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(putStrLn . show . solution2) octopodes
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solution1 :: [[Int]] -> Int
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solution1 m = snd (iterate flashSimulate (m, 0) !! 100)
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solution2 :: [[Int]] -> Int
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solution2 m = countUntil (all (all (==0)) . fst) flashSimulate (m, 0)
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flashSimulate :: ([[Int]], Int) -> ([[Int]], Int)
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flashSimulate (octopodes, flashes) =
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(refreshOctopodes exhaustedOctopodes, flashes + countExhaustedOctopodes exhaustedOctopodes)
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where
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exhaustedOctopodes = flashStep octopodes
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countExhaustedOctopodes = foldr (\l a -> length l + a) 0 . map (filter (> 9))
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refreshOctopodes = map (map (\o -> if o > 9 then 0 else o))
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flashStep :: [[Int]] -> [[Int]]
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flashStep = propagateFlashes . map (map (+1))
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where
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propagateFlashes :: [[Int]] -> [[Int]]
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propagateFlashes = until allExhausted flashOctopi
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where
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allExhausted :: [[Int]] -> Bool
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allExhausted = all (all (/= 10))
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flashOctopi :: [[Int]] -> [[Int]]
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flashOctopi m = map (map (incrementFlashing m))
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[[(x, y) | y <- [0..length (m !! x) - 1]] | x <- [0..length m - 1]]
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where
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incrementFlashing ::[[Int]] -> (Int, Int) -> Int
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incrementFlashing m' o
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| charge < 10 && newCharge > 10 = 10 -- Ensure we don't miss an increment
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| otherwise = charge + numFlashingNeighbors o
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where
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newCharge = charge + numFlashingNeighbors o
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charge = m' !!! o
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numFlashingNeighbors :: (Int, Int) -> Int
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numFlashingNeighbors = length . filter (\o -> (m !!! o) == 10) . (flip adjacent m)
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(!!!) :: [[Int]] -> (Int, Int) -> Int
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(!!!) m index = m !! (fst index) !! (snd index)
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countUntil :: (a -> Bool) -> (a -> a) -> a -> Int
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countUntil p f = call
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where
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call x
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| p x = 0
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| otherwise = call (f x) + 1
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adjacent :: (Int, Int) -> [[Int]] -> [(Int, Int)]
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adjacent (x, y) m = [(x+i, y+j) |
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i <- [-1..1],
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j <- [-1..1],
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-- (i, j) /= (0, 0),
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x+i >= 0,
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y+j >= 0,
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x+i < length m,
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y+j < length (m !! 0)]
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-- Tests
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testInput1 = [
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"5483143223",
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"2745854711",
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"5264556173",
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"6141336146",
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"6357385478",
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"4167524645",
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"2176841721",
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"6882881134",
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"4846848554",
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"5283751526"
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]
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parsedTestInput1 = map (map digitToInt) testInput1
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testInput2 = [
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"11111",
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"19991",
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"19191",
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"19991",
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"11111"
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]
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parsedTestInput2 = map (map digitToInt) testInput2
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test1 = solution1 parsedTestInput1
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test2 = solution2 parsedTestInput1
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