Add Day 2 solutions

README.md

@@ -3,7 +3,7 @@
 |Day|Stars|Day|Stars|
 |---|-----|---|-----|
 |01 |★ ★  |07 |     |
-|02 |     |08 |     |
+|02 |★    |08 |     |
 |03 |     |09 |     |
 |04 |     |10 |     |
 |05 |     |11 |     |

adventofcode2025.cabal

@@ -19,6 +19,7 @@ executable adventofcode2025
   main-is:             Main.hs
   default-language:    Haskell2010
   build-depends:       base >= 4.7 && < 5
+                     , split
   ghc-options:         -Wall
                        -Wcompat
                        -Widentities
@@ -30,3 +31,4 @@ executable adventofcode2025
                        -Wredundant-constraints
   other-modules:
     Day01
+    Day02

src/Day02.hs

@@ -0,0 +1,46 @@
+module Day02
+  ( day02_1,
+    day02_2
+  )
+where
+
+import Data.List (isInfixOf)
+import Data.List.Split (splitOn)
+
+sumInvalid :: [Int] -> Int
+sumInvalid = foldl addInvalid 0
+    where
+        addInvalid acc n
+            | odd (length (show n)) = acc
+            | let l2 = length (show n) `div` 2, take l2 (show n) == drop l2 (show n) = acc + n
+            | otherwise = acc
+
+sumInvalid' :: [Int] -> Int
+sumInvalid' = foldl addInvalid 0
+    where addInvalid acc n
+            | let s = drop 1 $ show n ++ show n, show n `isInfixOf` take (length s - 1) s = acc + n
+            | otherwise = acc
+            
+
+getRange :: String -> [Int]
+getRange r = [read (takeWhile (/= '-') r)..read $ drop 1 (dropWhile (/= '-') r)]
+
+parseInput :: IO [Int]
+parseInput = do
+    concatMap getRange . splitOn "," <$> readFile "input/day2.txt"
+
+day02_1 :: IO ()
+day02_1 = do
+  values <- parseInput
+  let result = sumInvalid values
+  putStrLn $
+    "Day 2, Puzzle 1 solution: "
+        ++ show result
+
+day02_2 :: IO ()
+day02_2 = do
+  values <- parseInput
+  let result = sumInvalid' values
+  putStrLn $
+    "Day 2, Puzzle 1 solution: "
+        ++ show result

src/Main.hs

@@ -1,6 +1,7 @@
 module Main (main) where
 
 import Day01 (day01_1, day01_2)
+import Day02 (day02_1, day02_2)
 import System.Environment (getArgs)
 
 main :: IO ()
@@ -12,7 +13,14 @@ main = do
     "1" : _ -> do
       day01_1
       day01_2
+    "2" : "1" : _ -> day02_1
+    "2" : "2" : _ -> day02_2
+    "2" : _ -> do
+      day02_1
+      day02_2
     "all" : _ -> do
       day01_1
       day01_2
+      day02_1
+      day02_2
     _ -> error "Not implemented"