Add Day 1, Puzzle 2 solution

README.md

@@ -2,7 +2,7 @@
 
 |Day|Stars|Day|Stars|
 |---|-----|---|-----|
-|01 |     |07 |     |
+|01 |★ ★  |07 |     |
 |02 |     |08 |     |
 |03 |     |09 |     |
 |04 |     |10 |     |

src/Day01.hs

@@ -1,5 +1,6 @@
 module Day01
   ( day01_1,
+    day01_2,
   )
 where
 
@@ -8,15 +9,28 @@ parseInput = do
   lines <$> readFile "input/day1.txt"
 
 rotate :: Int -> String -> Int
-rotate n ('L':xs) = (n - read xs) `mod` 100
-rotate n ('R':xs) = (n + read xs) `mod` 100
+rotate n ('L' : xs) = (n - read xs) `mod` 100
+rotate n ('R' : xs) = (n + read xs) `mod` 100
 rotate n _ = n
 
+rotate' :: Int -> String -> (Int, Int)
+rotate' 0 ('L' : xs) = (negate (read xs) `mod` 100, (read xs + 100) `div` 100 - 1)
+rotate' n ('L' : xs) = ((n - read xs) `mod` 100, (read xs - n + 100) `div` 100)
+rotate' n ('R' : xs) = ((n + read xs) `mod` 100, (read xs + n) `div` 100)
+rotate' n _ = (n, 0)
+
 getPassword :: Int -> Int -> [String] -> Int
 getPassword pass 0 [] = pass + 1
 getPassword pass _ [] = pass
-getPassword pass 0 (x:xs) = getPassword (pass + 1) (rotate 0 x) xs
-getPassword pass curr (x:xs) = getPassword pass (rotate curr x) xs
+getPassword pass 0 (x : xs) = getPassword (pass + 1) (rotate 0 x) xs
+getPassword pass curr (x : xs) = getPassword pass (rotate curr x) xs
+
+getPassword' :: Int -> Int -> [String] -> Int
+getPassword' pass _ [] = pass
+getPassword' pass curr (x : xs) = getPassword' newPass newVal xs
+  where
+    (newVal, nZero) = rotate' curr x
+    newPass = pass + nZero
 
 day01_1 :: IO ()
 day01_1 = do
@@ -25,3 +39,11 @@ day01_1 = do
   putStrLn $
     "Day 1, Puzzle 1 solution: "
       ++ show result
+
+day01_2 :: IO ()
+day01_2 = do
+  input <- parseInput
+  let result = getPassword' 0 50 input
+  putStrLn $
+    "Day 1, Puzzle 2 solution: "
+      ++ show result

src/Main.hs

@@ -1,6 +1,6 @@
 module Main (main) where
 
-import Day01 (day01_1)
+import Day01 (day01_1, day01_2)
 import System.Environment (getArgs)
 
 main :: IO ()
@@ -8,8 +8,11 @@ main = do
   args <- getArgs
   case args of
     "1" : "1" : _ -> day01_1
+    "1" : "2" : _ -> day01_2
     "1" : _ -> do
       day01_1
+      day01_2
     "all" : _ -> do
       day01_1
+      day01_2
     _ -> error "Not implemented"