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29 lines
1010 B
Haskell
29 lines
1010 B
Haskell
import Data.List
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move :: [(Int, Int)] -> Char -> [(Int, Int)]
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move ((x, y):xs) '>' = (x + 1, y):((x, y):xs)
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move ((x, y):xs) '<' = (x - 1, y):((x, y):xs)
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move ((x, y):xs) '^' = (x, y + 1):((x, y):xs)
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move ((x, y):xs) 'v' = (x, y - 1):((x, y):xs)
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houses :: [Char] -> [(Int, Int)]
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houses input = foldl move [(0, 0)] input
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foldlBoth :: (a -> b -> a) -> (a, a) -> [b] -> (a, a)
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foldlBoth f (l1, l2) (x1:(x2:xs)) = foldlBoth f (f l1 x1, f l2 x2) xs
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foldlBoth f (l1, l2) (x1:_) = foldlBoth f (f l1 x1, l2) []
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foldlBoth f (l1, l2) [] = (l1, l2)
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housesWithBot :: [Char] -> [(Int, Int)]
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housesWithBot input = santaHouses ++ botHouses
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where (santaHouses, botHouses) = foldlBoth move ([(0, 0)], [(0, 0)]) input
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uniqueHouses :: [(Int, Int)] -> [((Int, Int), Int)]
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uniqueHouses input = (map (\xs -> (head xs, length xs)) . group . sort) input
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day3part1 :: [Char] -> Int
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day3part1 input = length (uniqueHouses (houses input))
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day3part2 :: [Char] -> Int
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day3part2 input = length (uniqueHouses (housesWithBot input))
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