38 lines
1.1 KiB
Haskell
38 lines
1.1 KiB
Haskell
import Aoc
|
|
|
|
parseLine :: String -> [Bool]
|
|
parseLine = map toBool
|
|
where
|
|
toBool '.' = False
|
|
toBool '#' = True
|
|
|
|
countNeighbours :: [[Bool]] -> (Bool, Int)
|
|
countNeighbours [[a, b, c], [d, e, f], [g, h, i]] = (e, length (filter id [a, b, c, d, f, g, h, i]))
|
|
|
|
survives :: (Bool, Int) -> Bool
|
|
survives (False, n) = n == 3
|
|
survives (True, n) = n == 2 || n == 3
|
|
|
|
simulate :: [[Bool]] -> [[Bool]]
|
|
simulate = kernelMap (survives . countNeighbours) (Just False)
|
|
|
|
numOn :: [[Bool]] -> Int
|
|
numOn = sum . map (sum . map fromEnum)
|
|
|
|
doSimulate :: ([[Bool]] -> [[Bool]]) -> [[Bool]] -> Int
|
|
doSimulate simulate board = numOn $ iterate simulate board !! 100
|
|
|
|
part1 :: [[Bool]] -> Int
|
|
part1 = doSimulate simulate
|
|
|
|
part2 :: [[Bool]] -> Int
|
|
part2 = doSimulate simulate' . keepOn
|
|
where
|
|
updateFirst f (x:xs) = f x: xs
|
|
updateLast f (x:xs) = if null xs then [f x] else x: updateLast f xs
|
|
updateEnds f = updateFirst f . updateLast f
|
|
keepOn = updateEnds (updateEnds $ const True)
|
|
simulate' = keepOn . simulate
|
|
|
|
main :: IO ()
|
|
main = aocMain (map parseLine) part1 part2 |