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module Main where
import Data.Array.Unboxed
import Data.List (maximumBy, sortBy, sortOn, groupBy)
import Data.Ord (comparing)
-- import Data.Ratio
import Input
main :: IO ()
main = do
inp <- getInput 10
let h = length inp
w = length (head inp)
arr = array ((0, 0), (w-1, h-1)) [((x, y), c == '#') | (y, row) <- zip [0..] inp, (x, c) <- zip [0..] row]
:: UArray (Int, Int) Bool
asts = map fst (filter snd (assocs arr))
sight (a,b) (x,y) =
let dx = (x - a) `div` g
dy = (y - b) `div` g
g = gcd (abs (x - a)) (abs (y - b))
pts = [(a + i * dx, b + i * dy) | i <- [1..g-1]]
in all (not . (arr !)) pts
numVisible p = length (filter (\q -> q /= p && sight p q) asts)
-- (cent@(centx, centy), centNumVis) = maximumBy (comparing snd) (zip asts (map numVisible asts))
(cent@(centx, centy), centNumVis) = ((8, 3), 42)
print centNumVis
print cent
let -- atan2R' dy dx
-- | dy <= 0, dx < 0 = abs dy % abs dx : -inf -> 0
-- | dy > 0, dx < 0 = abs dy % abs dx : 0 -> inf
-- | dy > 0, dx == 0 = 0
-- | dy > 0, dx > 0 = abs dy % abs dx : inf -> 0
-- | dy <= 0, dx > 0 = abs dy % abs dx : 0 -> -inf
-- | dy < 0, dx == 0 = 1
-- | otherwise = undefined -- (dx, dy) == (0, 0)
threeLine (cx, cy) (a, b) (x, y) = (a - cx) * (y - cy) == (x - cx) * (b - cy)
distsq (a, b) (x, y) = (x - a) * (x - a) + (y - b) * (y - b)
otherAsts = sortOn (\(x, y) -> atan2 (fromIntegral (centx - x) :: Double) (fromIntegral (y - centy)))
(filter (/= cent) asts)
groups' = map (sortBy (comparing (distsq cent))) (groupBy (threeLine cent) otherAsts)
groups = last groups' : init groups'
zapRound l = (map head l, filter (not . null) (map tail l))
zapped = concat (takeWhile (not . null) (map fst (tail (iterate (zapRound . snd) (undefined, groups)))))
mapM_ print groups
print zapped
print (zapped !! 199)
-- let (n200x, n200y) = otherAsts !! 199
-- print (n200x * 100 + n200y)
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