advent19/src/advent19.hs

   1 -- import Debug.Trace
   2
   3 import Text.ParserCombinators.ReadP
   4 -- import Text.ParserCombinators.ReadP ((+++))
   5 import Data.Char (isDigit, isAlpha)
   6
   7 import qualified Data.IntMap.Strict as M
   8 import Data.IntMap.Strict ((!))
   9
  10 import Data.Functor (void)
  11 import Data.Either
  12
  13
  14 data Rule = Letter Char
  15           -- | Then2 Rule Rule
  16           -- | Then3 Rule Rule Rule
  17           | Then [Rule]
  18           | Or Rule Rule
  19           | See Int
  20           deriving (Show, Eq)
  21
  22 type RuleSet = M.IntMap Rule
  23
  24
  25 main :: IO ()
  26 main =
  27   do  text <- readFile "data/advent19.txt"
  28       -- print text
  29       let (rules, messages) = parse inputP text
  30       print $ part1 rules messages
  31       print $ part2 rules messages
  32       -- print $ part2 text
  33
  34 setup fname =
  35   do text <- readFile fname
  36      let (rules, messages) = parse inputP text
  37      let newRules = parse rulesP "8: 42 | 42 8\n11: 42 31 | 42 11 31"
  38      let updatedRules = M.union newRules rules
  39      let myParser = makeParser updatedRules (See 0)
  40      return (myParser, updatedRules, messages)
  41
  42
  43 part1 = countMatches
  44
  45 part2 rules messages = countMatches updatedRules messages
  46   where newRules = parse rulesP "8: 42 | 42 8\n11: 42 31 | 42 11 31"
  47         updatedRules = M.union newRules rules
  48
  49 countMatches rules messages
  50   = length $ filter ((== "") . snd) results
  51   where myParser = makeParser rules (See 0)
  52         results = concatMap (readP_to_S myParser) messages
  53
  54
  55 parse :: ReadP a -> String -> a
  56 parse parser str = fst $ head $ filter ((== "") . snd) $ readP_to_S parser str
  57
  58
  59 -- Generate the rules
  60
  61 makeParser :: RuleSet -> Rule -> ReadP ()
  62 makeParser m (Letter c) = void $ char c
  63 makeParser m (Then rs) = mapM_ (makeParser m) rs
  64 makeParser m (Or a b) = (makeParser m a) +++ (makeParser m b)
  65 makeParser m (See i) = makeParser m (m!i)
  66
  67
  68 -- Parse the input
  69
  70 rulesP = M.fromList <$> ruleP `sepBy` endOfLine
  71 ruleP = (,) <$> decimal <* (string ": ") <*> ruleBodyP
  72 ruleBodyP = choice [letterRuleP, orRuleP, thenRuleP, seeRuleP]
  73
  74 letterRuleP = Letter <$> between (string "\"") (string "\"") get
  75 orRuleP = Or <$> thenRuleP <* (string " | ") <*> thenRuleP
  76 thenRuleP = Then <$> seeRuleP `sepBy` (string " ")
  77 seeRuleP = See <$> decimal
  78
  79
  80 inputP = (,) <$> rulesP <* blankLines <*> messagesP
  81
  82 messagesP = (munch1 isAlpha) `sepBy` endOfLine
  83
  84 blankLines = skipMany1 endOfLine
  85
  86 decimal = read <$> many1 (satisfy isDigit)
  87 endOfLine = char '\n'