From fbc08a2e459a992ed0ad568f67f2a520bf163e0b Mon Sep 17 00:00:00 2001
From: Daniele Fucini <dfucini@gmail.com>
Date: Mon, 1 Dec 2025 21:00:45 +0100
Subject: [PATCH] Add Day 1, Puzzle 2 solution

---
 README.md    |  2 +-
 src/Day01.hs | 34 ++++++++++++++++++++++++++++------
 src/Main.hs  |  5 ++++-
 3 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index cdeaa62..9a1e159 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 |Day|Stars|Day|Stars|
 |---|-----|---|-----|
-|01 |     |07 |     |
+|01 |★ ★  |07 |     |
 |02 |     |08 |     |
 |03 |     |09 |     |
 |04 |     |10 |     |
diff --git a/src/Day01.hs b/src/Day01.hs
index 9cd710c..6c0df76 100644
--- a/src/Day01.hs
+++ b/src/Day01.hs
@@ -1,22 +1,36 @@
 module Day01
   ( day01_1,
+    day01_2,
   )
 where
 
 parseInput :: IO [String]
 parseInput = do
-    lines <$> readFile "input/day1.txt"
+  lines <$> 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
@@ -24,4 +38,12 @@ day01_1 = do
   let result = getPassword 0 50 input
   putStrLn $
     "Day 1, Puzzle 1 solution: "
-    ++ show result
+      ++ show result
+
+day01_2 :: IO ()
+day01_2 = do
+  input <- parseInput
+  let result = getPassword' 0 50 input
+  putStrLn $
+    "Day 1, Puzzle 2 solution: "
+      ++ show result
diff --git a/src/Main.hs b/src/Main.hs
index 8d31432..9206283 100644
--- a/src/Main.hs
+++ b/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"