From bab443b919e2142a963546a21479f5d393f4cdc1 Mon Sep 17 00:00:00 2001
From: eriedaberrie <eriedaberrie@gmail.com>
Date: Thu, 7 Dec 2023 23:10:02 -0800
Subject: [PATCH] 2023 day 8: add Haskell solution

---
 .gitignore      |  1 +
 2023/8/Main1.hs | 26 ++++++++++++++++++++++++++
 2023/8/Main2.hs | 31 +++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 2023/8/Main1.hs
 create mode 100644 2023/8/Main2.hs

diff --git a/.gitignore b/.gitignore
index 592f45e..a6db57c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@
 *data*.txt
 [Mm]ain
 [Mm]ain-[0-9]
+[Mm]ain[0-9]
 
 # Nix stuff
 result*
diff --git a/2023/8/Main1.hs b/2023/8/Main1.hs
new file mode 100644
index 0000000..f8ae9c5
--- /dev/null
+++ b/2023/8/Main1.hs
@@ -0,0 +1,26 @@
+import qualified Data.HashMap.Strict as HMS
+
+type DataMap = HMS.HashMap String (String, String)
+
+getDirection :: Char -> (a, a) -> a
+getDirection 'L' = fst
+getDirection 'R' = snd
+
+countTimes :: String -> DataMap -> Int
+countTimes directions m = countTimes' directions "AAA" 0
+  where
+    countTimes' (d:ds) s
+      | s == "ZZZ" = id
+      | otherwise  = countTimes' ds (getDirection d $ m HMS.! s) . succ
+
+getDataMap :: [String] -> DataMap
+getDataMap = HMS.fromList . map parseLine
+  where
+    parseLine l = (take 3 l, (take 3 $ drop 7 l, take 3 $ drop 12 l))
+
+main :: IO ()
+main = do
+  allLines <- lines <$> readFile "data.txt"
+  let directions = cycle $ head allLines
+      dataMap = getDataMap $ drop 2 allLines
+  print $ countTimes directions dataMap
diff --git a/2023/8/Main2.hs b/2023/8/Main2.hs
new file mode 100644
index 0000000..27dffde
--- /dev/null
+++ b/2023/8/Main2.hs
@@ -0,0 +1,31 @@
+import qualified Data.HashMap.Strict as HMS
+import Data.List (foldl1')
+
+type DataMap = HMS.HashMap String (String, String)
+
+getDirection :: Char -> (a, a) -> a
+getDirection 'L' = fst
+getDirection 'R' = snd
+
+countTimes :: String -> DataMap -> String -> Int
+countTimes directions m start = countTimes' directions start 0
+  where
+    countTimes' (d:ds) ss@(s:_)
+      | s == 'Z'  = id
+      | otherwise = countTimes' ds (getDirection d $ m HMS.! ss) . succ
+
+solve :: String -> DataMap -> Int
+solve directions m = foldl1' lcm $ map (countTimes directions m) $ filter ((== 'A') . head) $ HMS.keys m
+
+getDataMap :: [String] -> DataMap
+getDataMap = HMS.fromList . map parseLine
+  where
+    revTake3 = reverse . take 3
+    parseLine l = (revTake3 l, (revTake3 $ drop 7 l, revTake3 $ drop 12 l))
+
+main :: IO ()
+main = do
+  allLines <- lines <$> readFile "data.txt"
+  let directions = cycle $ head allLines
+      dataMap = getDataMap $ drop 2 allLines
+  print $ solve directions dataMap