From 79ed60a4f280321d9fc7c3a8bc1b2e0db705770e Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Tue, 3 Dec 2024 11:54:42 +0000
Subject: [Day 03] Done

---
 day03/day03.hs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 day03/day03.hs

(limited to 'day03/day03.hs')

diff --git a/day03/day03.hs b/day03/day03.hs
new file mode 100644
index 0000000..4082c24
--- /dev/null
+++ b/day03/day03.hs
@@ -0,0 +1,44 @@
+import Data.List
+import Data.List.Split
+import Text.Regex.TDFA
+import Text.Regex.TDFA.Text ()
+
+parse :: String -> Int
+parse str =
+  product $ map (read::String->Int) $ getAllTextMatches (str =~ "[0-9]+")
+
+part1 :: String -> Int
+part1 mem = 
+  sum $ map (parse) $ getAllTextMatches (mem =~ "mul\\([0-9]+,[0-9]+\\)")
+
+data Ins = Do | Dont | Mul Int Int deriving Show
+
+parse2 :: String -> Ins
+parse2 str
+  | third == '(' = Do
+  | third == 'n' = Dont
+  | otherwise = let (f:s:[]) = map (read::String->Int) $ getAllTextMatches (str =~ "[0-9]+") in
+                  Mul f s
+  where third = head $ tail $ tail str
+
+execute :: Bool -> Int -> [Ins] -> Int
+execute _ sum [] = sum
+execute _ sum (Do:rest) =
+  execute True sum rest
+execute _ sum (Dont:rest) =
+  execute False sum rest
+execute True sum (Mul x y:rest) =
+  execute True (sum + x * y) rest
+execute False sum (Mul x y:rest) =
+  execute False sum rest
+
+part2 :: String -> Int
+part2 mem = 
+  (execute True 0) $
+    map (parse2) $
+    getAllTextMatches (mem =~ "(mul\\([0-9]+,[0-9]+|do(n't)?\\()\\)")
+
+main = do
+  memory <- readFile "day03.input"
+  putStrLn ("Part 1: " ++ (show $ part1 memory))
+  putStrLn ("Part 2: " ++ (show $ part2 memory))
-- 
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