import Data.List.Split (splitOn)
import qualified Data.Set as S

type Coord = (Int, Int)

globalY :: Int
globalY = 2000000

parseCoord :: String -> Coord
parseCoord xs = (read $ init x, read y) where
    [x,y] = map (drop 2) $ splitOn " " xs

parseLine :: String -> (Coord, Coord)
parseLine xs = (sensor, beacon) where
    [sensor, beacon] = map (parseCoord . dropWhile (/='x'))$ splitOn ":" xs

manhattan :: Coord -> Coord -> Int
manhattan (a,b) (x,y) = abs (a-x) + abs (b-y)

allWithinRange :: Coord -> Coord -> S.Set Coord
allWithinRange sensor@(a,b) beacon@(x,y) = S.fromList $ filter (\c -> manhattan sensor c <= dist) all where
    minx = a - dist
    maxx = a + dist
    miny = b - dist
    maxy = b + dist
    dist = manhattan sensor beacon
    all = [(x,y) | x <- [minx..maxx], y <- [globalY]]

main :: IO ()
main = do
    x <- map parseLine . lines <$> getContents

    let beacons = S.fromList $ map snd x
    let reachable = foldr1 S.union $ map (uncurry allWithinRange) x

    let ys = S.size $ S.filter (\x -> snd x == globalY) (reachable S.\\ beacons)

    putStr "part 1: "
    print ys