feat: complete day 3

advent-of-haskell.cabal

@@ -11,7 +11,7 @@ build-type:    Simple
 common common
   default-language:   GHC2021
   ghc-options:        -Wall
-  default-extensions: RecordWildCards
+  default-extensions: RecordWildCards, OverloadedStrings
 
 executable runner
   import:         common

solutions/Days/Day03.hs

@@ -1,16 +1,39 @@
-module Days.Day03 (day03) where
+module Days.Day03 (day03, splitInto, commonItem) where
 
 import AOC (Solution (..))
 import qualified Data.Text as T
+import Data.List
+import Data.Maybe
+import Debug.Trace
 
 day03 :: Solution
 day03 = Solution parseInput part1 part2
 
-parseInput :: T.Text -> a
-parseInput = error "parseInput not defined for day 03"
+parseInput :: T.Text -> [[String]]
+parseInput input = go [] allLines
+  where
+    go acc [] = reverse acc
+    go acc xs = go (take 3 xs : acc) (drop 3 xs)
+    allLines = map T.unpack $ T.lines input
 
-part1 :: a -> Int
-part1 = error "part1 not defined for day 03"
+priority :: Char -> Int
+priority = (+1) . fromJust . flip elemIndex (['a'..'z'] ++ ['A'..'Z'])
 
-part2 :: a -> Int
-part2 = error "part2 not defined for day 03"
+splitInto :: Int -> [a] -> [[a]]
+splitInto s xs = go [] xs
+  where 
+    go acc [] = reverse acc
+    go acc xs' = go (take takeInt xs' : acc) (drop takeInt xs')
+    takeInt = round $ (fromIntegral $ length xs) / (fromIntegral s)
+
+commonItem :: Eq a => [[a]] -> [a]
+commonItem [] = []
+commonItem xs = foldl1' intersect xs
+
+part1 :: [[String]] -> Int
+part1 input = sum $ map (priority . head . commonItem . splitInto 2) (concat input)
+
+part2 :: [[String]] -> Int
+part2 input = sum $ map (priority . head . commonItem) input
+-- part2 input = sum $ map (sum . map (priority . head . commonItem . splitInto 2)) (traceShowId input)
+-- part2 input = traceShowId input