2024-25 in haskell

2024/25-Code_Chronicle/example

@@ -0,0 +1,40 @@
+#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####
+

2024/25-Code_Chronicle/first.hs

@@ -0,0 +1,66 @@
+-- requires cabal install --lib megaparsec parser-combinators heap vector
+module Main (main) where
+
+import           Control.Monad        (void, when)
+import           Data.Functor
+import qualified Data.List            as L
+import qualified Data.Map             as M
+import           Data.Maybe
+import           Data.Ord             (comparing)
+import           Data.Void            (Void)
+import           Text.Megaparsec
+import           Text.Megaparsec.Char
+
+import           Debug.Trace
+
+exampleExpectedOutput = 3
+
+data Schematic = Lock [Int] | Key [Int] deriving Show
+type Input = [Schematic]
+
+type Parser = Parsec Void String
+
+parseOne :: Parser Int
+parseOne = char '#' *> pure 1
+       <|> char '.' *> pure 0
+
+parseLine :: Parser [Int]
+parseLine = some parseOne
+
+encode :: [Int] -> [Int] -> [Int]
+encode [] []            = []
+encode (a:acc) (l:line) = a+l:encode acc line
+
+parseSchematic :: Parser Schematic
+parseSchematic = do
+  lines <- some (parseLine <* eol)
+  let code = L.foldl' encode [0, 0, 0, 0, 0] lines
+  pure $ (if (head $ head lines) == 1 then Lock else Key) code
+
+parseInput' :: Parser Input
+parseInput' = some (parseSchematic <* eol) <* eof
+
+parseInput :: String -> IO Input
+parseInput filename = do
+  input <- readFile filename
+  case runParser parseInput' filename input of
+    Left bundle  -> error $ errorBundlePretty bundle
+    Right input' -> return input'
+
+compute :: Input -> Int
+compute input = L.foldl' compute' 0 locks
+  where
+    keys  = [ k | k@(Key _)  <- input ]
+    locks = [ l | l@(Lock _) <- input ]
+    compute' :: Int -> Schematic -> Int
+    compute' i l = L.foldl' (computeOne l) i keys
+    computeOne :: Schematic -> Int -> Schematic -> Int
+    computeOne (Lock ls) i (Key ks) = i + if all (< 8) (encode ls ks) then 1 else 0
+
+main :: IO ()
+main = do
+  example <- parseInput "example"
+  let exampleOutput = compute example
+  when  (exampleOutput /= exampleExpectedOutput)  (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
+  input <- parseInput "input"
+  print $ compute input