Initial commit

2017/09/day9.hs

@@ -0,0 +1,38 @@
+#!/usr/bin/env stack
+-- stack --resolver lts-9.17 script
+
+import Data.List
+
+data Stream = Stream
+  { depth :: Int
+  , score :: Int
+  , ignoreNextChar :: Bool
+  , garbage :: Bool
+  , countGarbage :: Int
+  } deriving (Show, Eq)
+
+processChar :: Stream -> Char -> Stream
+processChar stream c =
+  if ignoreNextChar stream then
+    stream { ignoreNextChar = False }
+  else if garbage stream then
+    case c of
+      '!' -> stream { ignoreNextChar = True }
+      '>' -> stream { garbage = False }
+      _ -> stream { countGarbage = countGarbage stream + 1 }
+  else if c == '}' then
+    stream { depth = depth stream - 1, score = score stream + depth stream }
+  else if c == '{' then
+    stream { depth = depth stream + 1 }
+  else if c == '<' then
+    stream { garbage = True }
+  else stream
+
+processStream :: String -> Stream
+processStream = foldl' processChar (Stream 0 0 False False 0)
+
+main :: IO ()
+main = do
+  stream <- processStream <$> getContents
+  putStrLn . show $ score stream
+  putStrLn . show $ countGarbage stream