Add solution to day 5.

2025/aoc/aoc.cabal

@@ -93,6 +93,20 @@ executable day4
     , base >=4.7 && <5
   default-language: Haskell2010
 
+executable day5
+  main-is: Main.hs
+  other-modules:
+      Paths_aoc
+  autogen-modules:
+      Paths_aoc
+  hs-source-dirs:
+      app/day5
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      aoc
+    , base >=4.7 && <5
+  default-language: Haskell2010
+
 test-suite aoc-test
   type: exitcode-stdio-1.0
   main-is: Spec.hs

2025/aoc/app/day5/Main.hs

@@ -0,0 +1,75 @@
+module Main (main) where
+
+import Data.List (isPrefixOf, sort)
+
+type Range = (Int, Int)
+
+type FreshDatabase = [Range]
+
+takeWhileList :: ([a] -> Bool) -> [a] -> [a]
+takeWhileList _ [] = []
+takeWhileList f (x : xs)
+  | f (x : xs) = x : takeWhileList f xs
+  | otherwise = []
+
+splitOn :: (Eq a) => [a] -> [a] -> [[a]]
+splitOn x [] = []
+splitOn x xs =
+  let e = takeWhileList (not . isPrefixOf x) xs
+   in e : splitOn x (drop (length e + length x) xs)
+
+processRange :: String -> Range
+processRange s =
+  case splitOn "-" s of
+    [a, b] -> (read a :: Int, read b :: Int)
+    _ -> error "Invalid range!"
+
+isFresh :: FreshDatabase -> Int -> Bool
+isFresh [] _ = False
+isFresh ((start, end) : xs) v = start <= v && v <= end || isFresh xs v
+
+buildDatabase :: String -> FreshDatabase -> FreshDatabase
+buildDatabase range db = processRange range : db
+
+freshIngredients :: FreshDatabase -> [Int] -> [Int]
+freshIngredients db = filter (isFresh db)
+
+parseDatabase :: String -> FreshDatabase
+parseDatabase = foldr buildDatabase [] . lines
+
+parseIngredients :: String -> [Int]
+parseIngredients = map (\x -> read x :: Int) . lines
+
+parseInput :: [String] -> (FreshDatabase, [Int])
+parseInput [a, b] = (parseDatabase a, parseIngredients b)
+parseInput _ = error "Wrong input!"
+
+part1 :: IO ()
+part1 =
+  getContents
+    >>= print . length . uncurry freshIngredients . parseInput . splitOn "\n\n"
+
+data RangeEvent = StartEvent | StopEvent deriving (Eq, Ord, Show)
+
+rangeCoverage :: [Range] -> Int
+rangeCoverage =
+  (\(_, _, _, c) -> c)
+    . foldl countCoverage (0, 0, 0, 0)
+    . sort
+    . concatMap (\(s, e) -> [(s, StartEvent), (e, StopEvent)])
+  where
+    countCoverage :: (Int, Int, Int, Int) -> (Int, RangeEvent) -> (Int, Int, Int, Int)
+    countCoverage (_, lastEnd, 0, coverage) (start, StartEvent)
+      | start == lastEnd = (start + 1, lastEnd, 1, coverage)
+      | otherwise = (start, lastEnd, 1, coverage)
+    countCoverage (lastStart, lastEnd, n, coverage) (_, StartEvent) = (lastStart, lastEnd, n + 1, coverage)
+    countCoverage (lastStart, _, 1, coverage) (end, StopEvent) = (lastStart, end, 0, coverage + ((end + 1) - lastStart))
+    countCoverage (lastStart, lastEnd, n, coverage) (_, StopEvent) = (lastStart, lastEnd, n - 1, coverage)
+
+part2 :: IO ()
+part2 =
+  getContents
+    >>= print . rangeCoverage . fst . parseInput . splitOn "\n\n"
+
+main :: IO ()
+main = part2

2025/aoc/inputs/day5_test.txt

@@ -0,0 +1,11 @@
+3-5
+10-14
+16-20
+12-18
+
+1
+5
+8
+11
+17
+32

2025/aoc/package.yaml

@@ -73,6 +73,15 @@ executables:
     - -with-rtsopts=-N
     dependencies:
     - aoc
+  day5:
+    main:                Main.hs
+    source-dirs:         app/day5
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - aoc
 
 tests:
   aoc-test: