Overengineered Day3

adventofcode.cabal

@@ -14,6 +14,7 @@ library
   exposed-modules:
       AoC.Day1
       AoC.Day2
+      AoC.Day3
   other-modules:
       Paths_adventofcode
   hs-source-dirs:
@@ -22,6 +23,8 @@ library
   build-depends:
       attoparsec
     , base ==4.*
+    , extra
+    , split
     , text
   default-language: Haskell2010
 
@@ -36,5 +39,7 @@ executable adventofcode
       adventofcode
     , attoparsec
     , base ==4.*
+    , extra
+    , split
     , text
   default-language: Haskell2010

executable/Main.hs

@@ -2,6 +2,7 @@
 
 import AoC.Day1 as Day1
 import AoC.Day2 as Day2
+import AoC.Day3 as Day3
 
 import qualified Data.Text.IO as T (readFile)
 
@@ -17,3 +18,10 @@ main = do
   putStrLn $ show $ Day2.solveA input2
   putStrLn $ show $ Day2.solveB "A Y\nB X\nC Z"
   putStrLn $ show $ Day2.solveB input2
+
+  input3 <- T.readFile "./input/day3.txt"
+  let demoInput3 = "vJrwpWtwJgWrhcsFMMfFFhFp\njqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL\nPmmdzqPrVvPwwTWBwg\nwMqvLMZHhHMvwLHjbvcjnnSBnvTQFn\nttgJtRGJQctTZtZT\nCrZsJsPPZsGzwwsLwLmpwMDw"
+  putStrLn $ show $ Day3.solveA demoInput3
+  putStrLn $ show $ Day3.solveA input3
+  putStrLn $ show $ Day3.solveB demoInput3
+  putStrLn $ show $ Day3.solveB input3

input/day3.txt

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+WHClslcNNWcqNWlCZdcHsVrThBwBjbhDTDBhrvDZJTwm
+NWVqqcHHNpsNcNVdVlhCMlHQQMQQzLfzQPttFGPMLSLgtF

package.yaml

@@ -6,12 +6,15 @@ dependencies:
   - base == 4.*
   - text
   - attoparsec
+  - split
+  - extra
 
 library:
   source-dirs: src
   exposed-modules:
     - AoC.Day1
     - AoC.Day2
+    - AoC.Day3
 
 executable:
   source-dirs: executable

src/AoC/Day3.hs

@@ -0,0 +1,65 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module AoC.Day3 where
+
+import Data.Text (Text)
+import Data.Maybe (fromMaybe)
+import Data.Monoid (Sum(..), getSum)
+import Data.List.Split (chunksOf)
+import Data.Tuple.Extra (uncurry3)
+import qualified Data.Text as T
+
+valueMap :: [(Char, Int)]
+valueMap = zip (['a'..'z']++['A'..'Z']) [1..]
+
+breakInTwoEqualLengthSubStrings :: Text -> (Text,Text)
+breakInTwoEqualLengthSubStrings txt = T.splitAt (T.length txt `div` 2) txt
+
+findCommonItem :: Text -> Text -> Char
+findCommonItem _ "" = undefined
+findCommonItem compartment1 compartment2 =
+  if (c `T.elem` compartment1)
+  then c
+  else findCommonItem compartment1 (T.tail compartment2)
+  where
+    c = T.head compartment2
+
+
+solveAOnOne :: Text -> Int
+solveAOnOne = fromMaybe undefined
+            . flip lookup valueMap
+            . uncurry findCommonItem
+            . breakInTwoEqualLengthSubStrings
+
+solveA :: Text -> Int
+solveA = getSum . mconcat . map (Sum . solveAOnOne) . T.lines
+
+--------------------------------------------------------------------------------
+-- Part 2
+
+findCommonItem3 :: Text -> Text -> Text -> Char
+findCommonItem3 c1 c2 c3 = T.head $ go (go c1 c2) c3
+  where
+    go :: Text -> Text -> Text
+    go t1 = T.foldl (\acc c -> if c `T.elem` t1 then T.cons c acc else acc) ""
+
+tupleMeUp3 :: [[Text]] -> [(Text,Text,Text)]
+tupleMeUp3 = go []
+  where
+    go :: [(Text,Text,Text)] -> [[Text]] -> [(Text,Text,Text)]
+    go tuples [] = tuples
+    go tuples ([t1, t2, t3]:xs) = go ((t1,t2,t3):tuples) xs
+    go _ _ = undefined
+
+solveBOnOne :: (Text,Text,Text) -> Int
+solveBOnOne = fromMaybe undefined
+            . flip lookup valueMap
+            . uncurry3 findCommonItem3
+
+solveB :: Text -> Int
+solveB = getSum
+       . mconcat
+       . map (Sum . solveBOnOne)
+       . tupleMeUp3
+       . chunksOf 3
+       . T.lines