1 files changed, 43 insertions, 0 deletions
diff --git a/day05/day05.hs b/day05/day05.hs
new file mode 100644
index 0000000..9118cd2
--- /dev/null
+++ b/day05/day05.hs
@@ -0,0 +1,43 @@
+import Data.List
+import Data.List.Split
+
+type Rule = [Int]
+type Update = [Int]
+
+relevant :: Update -> Rule -> Bool
+relevant upd (b:a:[]) = (b `elem` upd) && (a `elem` upd)
+
+abides :: Update -> Rule -> Bool
+abides [] _ = False
+abides (h:t) r@(a:[])
+  | h == a = True
+  | otherwise = abides t r
+abides (h:t) r@(b:a:[])
+  | h == b = abides t [a]
+  | otherwise = abides t r
+
+middle :: [Int] -> Int
+middle arr = arr !! (length arr `div` 2)
+
+valid :: [Rule] -> Update -> Bool
+valid rules update =
+  all (abides update) $ filter (relevant update) rules
+
+part11 :: Int -> [Rule] -> [Update] -> Int
+part11 acc _ [] = acc
+part11 acc rules (h:t)
+  | valid rules h = part11 (acc + (middle h)) rules t
+  | otherwise     = part11 acc rules t
+
+part1 :: [Rule] -> [Update] -> Int
+part1 rules updates =
+  part11 0 rules updates
+
+main = do
+  file <- readFile "day05.input"
+  let lns = lines file
+      rulesin:updatesin:[] = splitOn [""] lns
+      rules = map (map (read::String->Int)) $ map (splitOn "|") rulesin
+      updates = map (map (read::String -> Int)) $ map (splitOn ",") updatesin
+  putStrLn ("Part 1: " ++ (show $ part1 rules updates))
+  --putStrLn ("Part 2: " ++ (show $ part2 fst sec))