48 lines
1.2 KiB
Haskell
48 lines
1.2 KiB
Haskell
import Control.Arrow
|
|
import Control.Lens
|
|
import Data.Function
|
|
import Data.Ix
|
|
import Data.List
|
|
import Data.Ord
|
|
import Linear.V2
|
|
|
|
main :: IO ()
|
|
main = interact $ show . (day11 1 &&& day11 999999) . parse . lines
|
|
|
|
day11 :: V2 Int -> [V2 Int] -> Int
|
|
day11 n = (`div` 2) . sum . f . (expandBy n =<< findEmptyRows)
|
|
where
|
|
f xs = [sum $ abs $ x - y | x <- xs, y <- xs]
|
|
|
|
parse :: [String] -> [V2 Int]
|
|
parse =
|
|
map fst .
|
|
filter ((== '#') . snd) . concat . zipWith (map . f) [0 ..] . map (zip [0 ..])
|
|
where
|
|
f x (y, z) = (V2 y x, z)
|
|
|
|
expandBy :: V2 Int -> [V2 Int] -> [V2 Int] -> [V2 Int]
|
|
expandBy _ [] input = input
|
|
expandBy n (d:ds) input =
|
|
expandBy n (map (moveCoord n d) ds) (map (moveCoord n d) input)
|
|
|
|
findEmptyRows :: [V2 Int] -> [V2 Int]
|
|
findEmptyRows input =
|
|
map flipV2 (findEmptyRows $ map flipV2 input) ++ findEmptyRows input
|
|
where
|
|
findEmptyRows = deleteFirstsBy ((==) `on` view _x) b
|
|
b = range (V2 0 0, set _y 0 maxP)
|
|
maxP = maximumBy (comparing (view _x)) input
|
|
flipV2 (V2 x y) = V2 y x
|
|
|
|
moveCoord :: V2 Int -> V2 Int -> V2 Int -> V2 Int
|
|
moveCoord n x y =
|
|
if y ^. p >= x ^. p
|
|
then y + n * signum x
|
|
else y
|
|
where
|
|
p =
|
|
if x ^. _x == 0
|
|
then _y
|
|
else _x
|