Regex...

app/3.hs

@@ -1,15 +1,32 @@
 {-# LANGUAGE LambdaCase #-}
 module Main where
 
-import Data.Functor
+import Text.Regex.TDFA
+import Data.List.Split
 
-parse = undefined
+e :: [String] ->  [(Int,Int)]
+e = ((\case
+             [a,b] -> (read a, read b)
+             err -> error $ "Parsing failed on: " ++ show err
+         ) . splitWhen (== ',') . init . drop 4 <$>)
 
-solve1 = undefined
+parse1 :: String -> [(Int,Int)]
+parse1 =  e . getAllTextMatches . (=~ "mul\\([[:digit:]]+,[[:digit:]]+\\)")
 
-solve2 = undefined
+
+parse2 :: String -> [(Int,Int)]
+parse2 =
+  let h [] = []
+      h  a = let (t,t') = span (/= "don't()") a in t ++ g t'
+      g [] = []
+      g  a = h . dropWhile (== "do()") $ dropWhile (/= "do()") a in
+  e . filter (/= "do()") . h .
+  getAllTextMatches . (=~ "mul\\([[:digit:]]+,[[:digit:]]+\\)|do\\(\\)|don't\\(\\)")
+
+solve ::  [(Int,Int)] -> Int
+solve = foldr ((+) . uncurry (*)) 0
 
 main :: IO ()
-main = readFile "inputs/3" <&> parse >>= \i ->
-       print (solve1 i) >>
-       print (solve2 i)
+main = readFile "inputs/3" >>= \i ->
+       print (solve $ parse1 i) >>
+       print (solve $ parse2 i)