Day 10: Hoof It
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Haskell
Cool task, nothing to optimize
import Control.Arrow
import Data.Array.Unboxed (UArray)
import Data.Set (Set)
import qualified Data.Char as Char
import qualified Data.List as List
import qualified Data.Set as Set
import qualified Data.Array.Unboxed as UArray
parse :: String -> UArray (Int, Int) Int
parse s = UArray.listArray ((1, 1), (n, m)) . map Char.digitToInt . filter (/= '\n') $ s
where
n = takeWhile (/= '\n') >>> length $ s
m = filter (== '\n') >>> length >>> pred $ s
reachableNeighbors :: (Int, Int) -> UArray (Int, Int) Int -> [(Int, Int)]
reachableNeighbors p@(py, px) a = List.filter (UArray.inRange (UArray.bounds a))
>>> List.filter ((a UArray.!) >>> pred >>> (== (a UArray.! p)))
$ [(py-1, px), (py+1, px), (py, px-1), (py, px+1)]
distinctTrails :: (Int, Int) -> UArray (Int, Int) Int -> Int
distinctTrails p a
| a UArray.! p == 9 = 1
| otherwise = flip reachableNeighbors a
>>> List.map (flip distinctTrails a)
>>> sum
$ p
reachableNines :: (Int, Int) -> UArray (Int, Int) Int -> Set (Int, Int)
reachableNines p a
| a UArray.! p == 9 = Set.singleton p
| otherwise = flip reachableNeighbors a
>>> List.map (flip reachableNines a)
>>> Set.unions
$ p
findZeros = UArray.assocs
>>> filter (snd >>> (== 0))
>>> map fst
part1 a = findZeros
>>> map (flip reachableNines a)
>>> map Set.size
>>> sum
$ a
part2 a = findZeros
>>> map (flip distinctTrails a)
>>> sum
$ a
main = getContents
>>= print
. (part1 &&& part2)
. parse
