115 lines
3.3 KiB
Haskell
115 lines
3.3 KiB
Haskell
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import Data.List (find, transpose)
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import qualified Data.Set as Set
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import qualified Data.Text as Text
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import qualified Data.Text.IO as Text
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countVisibleTrees ::
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[[Int]] -> [Int] -> Int -> (Set.Set (Int, Int)) -> (Set.Set (Int, Int))
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countVisibleTrees [] _ _ seen = seen
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countVisibleTrees (row:rows) maxTrees depth seen =
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countVisibleTrees
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rows
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(zipWith (\x y -> max x y) row maxTrees)
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(depth + 1)
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(foldl
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(\acc x -> Set.insert x acc)
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seen
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(zipWith
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(\i x ->
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if x == 1
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then (depth, i)
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else (0, 0))
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[0 ..]
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(zipWith
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(\x y ->
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if x > y
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then 1
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else 0)
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row
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maxTrees)))
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treeScore :: [[Int]] -> (Int, Int) -> Int -> Int -> [Int]
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treeScore digits (x, y) width height =
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let currentHeight = ((digits !! y) !! x)
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in [ (case (find
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(\x -> (digits !! y) !! x >= currentHeight)
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[(x + 1) .. (width - 1)]) of
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Just value -> (value - x)
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Nothing -> (width - x - 1))
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, (case (find
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(\x -> (digits !! y) !! x >= currentHeight)
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(reverse [0 .. (x - 1)])) of
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Just value -> (x - value)
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Nothing -> x)
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, (case (find
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(\y -> (digits !! y) !! x >= currentHeight)
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(reverse [0 .. (y - 1)])) of
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Just value -> (y - value)
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Nothing -> y)
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, (case (find
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(\y -> (digits !! y) !! x >= currentHeight)
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[(y + 1) .. (height - 1)]) of
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Just value -> (value - y)
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Nothing -> (height - y - 1))
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]
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getDigitsFromString :: String -> [Int]
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getDigitsFromString = map (read . (: ""))
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rotl :: [[Int]] -> [[Int]]
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rotl = reverse . transpose
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rotr :: [[Int]] -> [[Int]]
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rotr = transpose . reverse
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main = do
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ls <- fmap Text.lines (Text.readFile "input")
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let digits = map (getDigitsFromString . Text.unpack) ls
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let height = length digits
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let width = length (head digits)
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let topDownSeen =
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countVisibleTrees digits (take width (repeat (-1))) 0 Set.empty
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let rightLeftSeen =
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Set.map
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(\x -> ((snd x), width - (fst x) - 1))
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(countVisibleTrees
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(rotl digits)
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(take height (repeat (-1)))
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0
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Set.empty)
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let downTopSeen =
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Set.map
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(\x -> (height - (fst x) - 1, (snd x)))
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(countVisibleTrees
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(reverse digits)
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(take width (repeat (-1)))
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0
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Set.empty)
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let leftRightSeen =
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Set.map
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(\x -> (height - (snd x) - 1, (fst x)))
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(countVisibleTrees
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(rotr digits)
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(take height (repeat (-1)))
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0
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Set.empty)
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let allSeen =
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(foldl
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(\acc x -> Set.union acc x)
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Set.empty
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[topDownSeen, rightLeftSeen, downTopSeen, leftRightSeen])
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print (Set.size allSeen)
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print
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(maximum
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(map
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(\y ->
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maximum
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(map
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(\x ->
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(foldl
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(\acc x -> acc * x)
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1
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(treeScore digits (x, y) width height)))
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[0 .. (width - 1)]))
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[0 .. (height - 1)]))
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