Add Day 3, Puzzle 1 solution

adventofcode2025.cabal

@@ -32,3 +32,4 @@ executable adventofcode2025
   other-modules:
     Day01
     Day02
+    Day03

src/Day03.hs

@@ -0,0 +1,25 @@
+module Day03
+  ( day03_1,
+  )
+where
+
+getBankJoltage :: String -> Int
+getBankJoltage bank = read [x, y]
+    where x = maximum $ init bank
+          y = maximum bank'
+          bank' = drop 1 $ dropWhile (/= x) bank
+
+getTotalJoltage :: [String] -> Int
+getTotalJoltage banks = sum $ map getBankJoltage banks
+
+parseInput :: IO [String]
+parseInput = do
+  lines <$> readFile "input/day3.txt"
+
+day03_1 :: IO ()
+day03_1 = do
+  banks <- parseInput
+  let joltage = getTotalJoltage banks
+  putStrLn $
+    "Day 3, Puzzle 1 solution: "
+      ++ show joltage

src/Main.hs

@@ -2,6 +2,7 @@ module Main (main) where
 
 import Day01 (day01_1, day01_2)
 import Day02 (day02_1, day02_2)
+import Day03 (day03_1)
 import System.Environment (getArgs)
 
 main :: IO ()
@@ -18,9 +19,13 @@ main = do
     "2" : _ -> do
       day02_1
       day02_2
+    "3" : "1" : _ -> day03_1
+    "3" : _ -> do
+      day03_1
     "all" : _ -> do
       day01_1
       day01_2
       day02_1
       day02_2
+      day03_1
     _ -> error "Not implemented"