Day 8! Took me longer than I'd like to admit

2022/aoc2022.cabal

@@ -9,4 +9,4 @@ executable aoc2022
     build-depends:    base ^>=4.16.2.0, split ^>=0.2.3.5, regex-tdfa ^>=1.3.2, containers ^>=0.6.6
     hs-source-dirs:   app
     default-language: Haskell2010
-    other-modules:    Day1.Main Day2.Main Day3.Main Day4.Main Day5.Main Day6.Main Day7.Main
+    other-modules:    Day1.Main Day2.Main Day3.Main Day4.Main Day5.Main Day6.Main Day7.Main, Day8.Main

2022/app/Day8/Main.hs

@@ -0,0 +1,59 @@
+module Day8.Main where
+
+import System.IO
+import Data.List
+
+main :: IO ()
+main = do
+    putStrLn "Day 8"
+    
+    handle <- openFile "app/Day8/input" ReadMode
+    contents <- hGetContents handle
+
+    let r1 = part1 contents
+    putStrLn $ "part 1: " ++ show r1
+
+    let r2 = part2 contents
+    putStrLn $ "part 2: " ++ show r2
+
+type Tree = (Int,[Int],[Int],[Int],[Int]) -- Self, N, E, S, W
+
+enumerate :: [a] -> [(Int, a)]
+enumerate = zip [0..]
+
+parseData :: String -> [[Int]]
+parseData contents = (map . map) (read . singleton :: Char -> Int) $ lines contents
+
+toTrees :: [[Int]] -> [Tree]
+toTrees rows = [(tree, north r c, east r c, south r c, west r c) | (r, line) <- enumerate rows, (c, tree) <- enumerate line]
+    where
+        columns = transpose rows
+        east r c = drop (c + 1) $ rows !! r
+        west r c = reverse $ take c $ rows !! r
+        north r c = reverse $ take r $ columns !! c
+        south r c = drop (r + 1) $ columns !! c
+
+isVisible :: Int -> [Int] -> Bool
+isVisible _ [] = True
+isVisible t ts = all (< t) ts
+
+invisibleFromOutside :: Tree -> Bool
+invisibleFromOutside (t,n,e,s,w) = all (not . isVisible t) [n,e,s,w]
+
+part1 :: String -> Int
+part1 = length . filter (not . invisibleFromOutside) . toTrees . parseData
+
+-- Includive version of takeWhile (because lentgh takeWhile + 1 doesn't work for when the outer border is the reason you can't see further)
+takeWhileI :: (a -> Bool) -> [a] -> [a]
+takeWhileI _ [] = []
+takeWhileI p (x:xs) =
+  x : if p x then takeWhileI p xs else []
+
+viewingDistance :: Int -> [Int] -> Int
+viewingDistance t ts = length $ takeWhileI (< t) ts
+
+scenicScore :: Tree -> Int
+scenicScore (t,n,e,s,w) = product $ map (viewingDistance t) [n,e,s,w]
+
+part2 :: String -> Int
+part2 = maximum . map scenicScore . toTrees . parseData

2022/app/Day8/example

@@ -0,0 +1,5 @@
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2022/app/Day8/input

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2022/app/Main.hs

@@ -7,6 +7,7 @@ import qualified Day4.Main as Day4
 import qualified Day5.Main as Day5
 import qualified Day6.Main as Day6
 import qualified Day7.Main as Day7
+import qualified Day8.Main as Day8
 
 main :: IO ()
 main = do
@@ -17,3 +18,4 @@ main = do
     Day5.main
     Day6.main
     Day7.main
+    Day8.main