2021/6.hs


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module Main where

import qualified Data.Array as A
import Numeric.Natural

import Input
import Util


main :: IO ()
main = do
    inp <- map read . toList . splitOn (== ',') . head <$> getInput 6
    let evolve :: A.Array Int Natural -> A.Array Int Natural
        evolve arr = A.accumArray (+) 0 (0, 8) $
            [(8, arr A.! 0), (6, arr A.! 0)] ++
            [(i, arr A.! (i + 1)) | i <- [0..7]]
        initState = A.accumArray (+) 0 (0, 8) [(i, 1) | i <- inp]
        after n = sum (A.elems (iterate evolve initState !! n))
    print (after 80)
    print (after 256)