Refactor code

src/Day02.hs

@@ -0,0 +1,37 @@
+module Day02
+  ( day02_1,
+    day02_2,
+  )
+where
+
+import Control.Monad
+import Data.List (sort, sortBy)
+import Data.Ord
+
+isSafe :: [Int] -> Bool
+isSafe xs = (isAscending xs || isDescending xs) && maximum distances <= 3 && minimum distances >= 1
+  where
+    isAscending x = x == sort x
+    isDescending x = x == sortBy (comparing Down) x
+    distances = map abs $ zipWith (-) xs (drop 1 xs)
+
+removeLevel :: [Int] -> [[Int]]
+removeLevel xs = filter (\x -> length x == l) $ filterM (const [True, False]) xs
+  where
+    l = length xs - 1
+
+day02_1 :: IO ()
+day02_1 = do
+  contents <- lines <$> readFile "input/day2.txt"
+  let reports = map read . words <$> contents
+  putStrLn $
+    "Day 2, Puzzle 1 solution: "
+      ++ show (length $ filter isSafe reports)
+
+day02_2 :: IO ()
+day02_2 = do
+  contents <- lines <$> readFile "input/day2.txt"
+  let reports = map read . words <$> contents
+  putStrLn $
+    "Day 2, Puzzle 2 solution: "
+      ++ show (length . filter (any isSafe) $ map removeLevel reports)