Day 6, Part 2
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@ -11,64 +11,54 @@ getDirection '>' = R
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getDirection 'v' = D
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getDirection '<' = L
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getStartPositionition :: Char -> Grid -> Position
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getStartPositionition c grid = (x, y)
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where x = fromMaybe (-1) . elemIndex True . map (isJust . elemIndex c) $ grid
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y = if x == -1
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then -1
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else fromMaybe (-1) . elemIndex c $ grid !! x
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getStartPosition:: Char -> Grid -> Position
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getStartPosition c grid = (x, y)
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where x = fromMaybe (-1) . elemIndex True . map (isJust . elemIndex c) $ grid
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y = if x == -1 then -1 else fromMaybe (-1) . elemIndex c $ grid !! x
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getGridVal :: Position -> Grid -> Char
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getGridVal (x, y) grid = (grid !! x) !! y
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moveUp :: Position -> Position
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moveUp (x, y) = (x - 1, y)
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moveDown :: Position -> Position
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moveDown (x, y) = (x + 1, y)
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moveLeft :: Position -> Position
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moveLeft (x, y) = (x, y - 1)
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moveRight :: Position -> Position
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moveRight (x, y) = (x, y + 1)
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isInside :: Position -> Grid -> Bool
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isInside (x, y) grid = x >= 0 && y >= 0 && x < length grid && y < length (head grid)
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getNextPosition :: Position -> Direction -> Grid -> (Position, Direction)
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getNextPosition (x, y) U grid = let newPos = moveUp (x, y)
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in if newPos `isInside` grid && getGridVal newPos grid == '#'
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then (moveRight (x, y), R)
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else (newPos, U)
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getNextPosition (x, y) R grid = let newPos = moveRight (x, y)
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in if newPos `isInside` grid && getGridVal newPos grid == '#'
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then (moveDown (x, y), D)
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else (newPos, R)
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getNextPosition (x, y) D grid = let newPos = moveDown (x, y)
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in if newPos `isInside` grid && getGridVal newPos grid == '#'
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then (moveLeft (x, y), L)
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else (newPos, D)
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getNextPosition (x, y) L grid = let newPos = moveLeft (x, y)
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in if newPos `isInside` grid && getGridVal newPos grid == '#'
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then (moveUp (x, y), U)
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else (newPos, L)
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getNextPosition (x, y) U grid = let newPos = (x - 1, y)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) R grid
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else (newPos, U)
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getNextPosition (x, y) R grid = let newPos = (x, y + 1)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) D grid
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else (newPos, R)
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getNextPosition (x, y) D grid = let newPos = (x + 1, y)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) L grid
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else (newPos, D)
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getNextPosition (x, y) L grid = let newPos = (x, y - 1)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) U grid
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else (newPos, L)
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markVisited :: Position -> Grid -> Grid
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markVisited (x, y) grid = let row = grid !! x
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newRow = take y row ++ ['X'] ++ drop (y + 1) row
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in take x grid ++ [newRow] ++ drop (x + 1) grid
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markVisited :: Position -> Char -> Grid -> Grid
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markVisited (x, y) c grid = let row = grid !! x
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newRow = take y row ++ [c] ++ drop (y + 1) row
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in take x grid ++ [newRow] ++ drop (x + 1) grid
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visitGrid :: Position -> Direction -> Grid -> Grid
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visitGrid (x, y) direction grid = let newGrid = markVisited (x, y) grid
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(newPosition, newDirection) = getNextPosition (x, y) direction grid
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in if newPosition `isInside` newGrid
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then visitGrid newPosition newDirection newGrid
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visitGrid (x, y) direction grid = let newGrid = markVisited (x, y) 'X' grid
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(nextPosition, newDirection) = getNextPosition (x, y) direction grid
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in if nextPosition `isInside` newGrid
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then visitGrid nextPosition newDirection newGrid
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else newGrid
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main = do
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contents <- lines <$> readFile "day6.txt"
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let (x, y) = (\w x y z -> head $ filter ((>= 0) . fst) [w, x, y, z]) <$> getStartPositionition 'v' <*> getStartPositionition '^'
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<*> getStartPositionition '<' <*> getStartPositionition '>' $ contents
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let (x, y) = (\w x y z -> head $ filter ((>= 0) . fst) [w, x, y, z]) <$> getStartPosition 'v' <*> getStartPosition '^'
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<*> getStartPosition '<' <*> getStartPosition '>' $ contents
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direction = getDirection $ (contents !! x) !! y
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print . length . filter (== 'X') . concat $ visitGrid (x, y) direction contents
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91
Day6/puzzle2.hs
Normal file
91
Day6/puzzle2.hs
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@ -0,0 +1,91 @@
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import Data.List (elemIndex)
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import Data.Maybe (isJust, fromMaybe)
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type Grid = [String]
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type Position = (Int, Int)
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data Direction = U | R | D | L deriving Eq
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getDirection :: Char -> Direction
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getDirection '^' = U
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getDirection '>' = R
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getDirection 'v' = D
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getDirection '<' = L
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printDirection :: Direction -> Char
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printDirection U = '^'
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printDirection R = '>'
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printDirection D = 'v'
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printDirection L = '<'
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getStartPosition :: Char -> Grid -> Position
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getStartPosition c grid = (x, y)
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where x = fromMaybe (-1) . elemIndex True . map (isJust . elemIndex c) $ grid
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y = if x == -1 then -1 else fromMaybe (-1) . elemIndex c $ grid !! x
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getGridVal :: Position -> Grid -> Char
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getGridVal (x, y) grid = (grid !! x) !! y
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isInside :: Position -> Grid -> Bool
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isInside (x, y) grid = x >= 0 && y >= 0 && x < length grid && y < length (head grid)
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getNextPosition :: Position -> Direction -> Grid -> (Position, Direction)
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getNextPosition (x, y) U grid = let newPos = (x - 1, y)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) R grid
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else (newPos, U)
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getNextPosition (x, y) R grid = let newPos = (x, y + 1)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) D grid
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else (newPos, R)
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getNextPosition (x, y) D grid = let newPos = (x + 1, y)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) L grid
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else (newPos, D)
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getNextPosition (x, y) L grid = let newPos = (x, y - 1)
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gridVal = getGridVal newPos grid
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in if newPos `isInside` grid && gridVal == '#'
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then getNextPosition (x, y) U grid
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else (newPos, L)
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markVisited :: Position -> Char -> Grid -> Grid
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markVisited (x, y) c grid = let gridVal = getGridVal (x, y) grid
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in if gridVal == '#' || gridVal == '^' || gridVal == '>' || gridVal == 'v' || gridVal == '<'
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then grid
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else let row = grid !! x
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newRow = take y row ++ [c] ++ drop (y + 1) row
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in take x grid ++ [newRow] ++ drop (x + 1) grid
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visitGrid :: Position -> Direction -> Grid -> Grid
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visitGrid (x, y) direction grid = let newGrid = markVisited (x, y) 'X' grid
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(nextPosition, newDirection) = getNextPosition (x, y) direction grid
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in if nextPosition `isInside` newGrid
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then visitGrid nextPosition newDirection newGrid
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else newGrid
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checkGridLoop :: Position -> Direction -> Grid -> Bool
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checkGridLoop startPosition direction grid = let (nextPosition, newDirection) = getNextPosition startPosition direction grid
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newDirectionChar = printDirection newDirection
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newGrid = markVisited nextPosition newDirectionChar grid
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in if not $ nextPosition `isInside` grid
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then False
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else if getGridVal nextPosition grid == newDirectionChar
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then True
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else checkGridLoop nextPosition newDirection newGrid
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setGridObstacles :: Position -> Grid -> [Grid]
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setGridObstacles startPosition grid = let positions = [ (x, y) | x <- [0..(length grid - 1)], y <- [0..(length (head grid) - 1)], (x, y) /= startPosition, getGridVal (x, y) grid == 'X' ]
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in zipWith (`markVisited` '#') positions (replicate (length positions) grid)
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main = do
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contents <- lines <$> readFile "day6.txt"
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let (x, y) = (\w x y z -> head $ filter ((>= 0) . fst) [w, x, y, z]) <$> getStartPosition 'v' <*> getStartPosition '^'
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<*> getStartPosition '<' <*> getStartPosition '>' $ contents
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direction = getDirection $ (contents !! x) !! y
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grid = visitGrid (x, y) direction contents
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gridObstacles = setGridObstacles (x, y) grid
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loops = filter (checkGridLoop (x, y) direction) gridObstacles
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print $ length loops
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