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