Solve day 5 part 1

haskell/Puzzles/Day5.hs

@@ -1,15 +1,42 @@
 module Puzzles.Day5 (puzzle) where
 
+import Control.Monad
+import Data.Functor
+import Data.List.Extra
+import Data.Maybe
+import Data.Text.Lazy qualified as TL
 import Puzzle
+import Text.Megaparsec hiding (some)
+import Text.Megaparsec.Char
+import Text.Megaparsec.Char.Lexer qualified as Lex
 
 puzzle :: Puzzle
 puzzle =
     Puzzle
         { number = 5
-        , parser = pure ()
+        , parser = do
+            ranges <- flip sepEndBy newline $ Range <$> Lex.decimal <* single '-' <*> Lex.decimal
+            void newline
+            vals <- sepEndBy Lex.decimal newline
+            pure (ranges, vals)
         , parts =
-            [ \() ->
-                "TODO"
+            [ \(ranges, vals) ->
+                TL.show
+                    . length
+                    . map fst
+                    . filter (notNull . snd)
+                    $ map
+                        (\v -> (v, mapMaybe (\r -> guard (isInRange v r) $> r) ranges))
+                        vals
             ]
         , extraTests = mempty
         }
+
+data Range = Range
+    { lower :: Int
+    , upper :: Int
+    }
+    deriving (Eq, Ord, Show)
+
+isInRange :: Int -> Range -> Bool
+isInRange n r = n >= r.lower && n <= r.upper

outputs/real/5/1

@@ -0,0 +1 @@
+874