day3 done

AoC2022.cabal

@@ -48,3 +48,17 @@ executable Day2
                     , safe
     hs-source-dirs:   day2
     default-language: Haskell2010
+
+executable Day3
+    main-is:          Main.hs
+
+    -- Modules included in this executable, other than Main.
+    -- other-modules:
+
+    -- LANGUAGE extensions used by modules in this package.
+    -- other-extensions:
+    build-depends:    base ^>=4.14.3.0
+                    , safe
+                    , extra
+    hs-source-dirs:   day3
+    default-language: Haskell2010

day2/Main.hs

@@ -92,13 +92,3 @@ result 'X' = Loss
 result 'Y' = Draw
 result 'Z' = Win
 result c = error $ "malformed Input: "<> show c
-
--- | Split a list into sublists delimited by the given element.
---
--- From: https://hackage.haskell.org/package/haskell-gi-0.26.2/docs/src/Data.GI.CodeGen.Util.html#splitOn
-splitOn :: Eq a => a -> [a] -> [[a]]
-splitOn x xs = go xs []
-    where go [] acc = [reverse acc]
-          go (y : ys) acc = if x == y
-                            then reverse acc : go ys []
-                            else go ys (y : acc)

day3/Main.hs

@@ -0,0 +1,52 @@
+{-# LANGUAGE LambdaCase #-}
+module Main where
+
+import Data.List as L
+import Data.Bifunctor
+import Data.Char
+import Data.Maybe
+import Data.List.Extra
+import Safe
+
+data InputOptions = SumPrios
+                  | SumGroups
+                  | Quit
+
+
+getInput :: IO InputOptions
+getInput = do
+  putStrLn "Sum Prios or Quit? (s/g/q)"
+  getLine >>= \case
+       "s" -> return SumPrios
+       "g" -> return SumGroups
+       "q" -> return Quit
+       _   -> putStrLn "not understood" >> getInput
+
+main :: IO ()
+main = getInput >>= \case
+    Quit -> putStrLn "bye!"
+    SumPrios -> interact $
+          (<>"\n")
+        . show
+        . sum
+        . fmap turnIntoPrios
+        . lines
+    SumGroups -> interact $
+          (<>"\n")
+        . show
+        . sum
+        . fmap turnIntoGroup
+        . chunksOf 3
+        . lines
+
+turnIntoPrios :: String -> Integer
+turnIntoPrios l = maximum . fmap toPrio . uncurry intersect . bimap sort sort . splitAt (length l `div` 2) $ l
+
+turnIntoGroup :: [String] -> Integer
+turnIntoGroup [a,b,c] = maximum . fmap toPrio $ intersect a (b `intersect` c)
+
+toPrio :: Char -> Integer
+toPrio x
+  | isAsciiLower x = toInteger $ ord x - ord 'a' + 1
+  | isAsciiUpper x = toInteger $ ord x - ord 'A' + 27
+  | otherwise      = error "malformed input"