Day 13

[advent-of-code-17.git] / src / advent13 / advent13.hs

diff --git a/src/advent13/advent13.hs b/src/advent13/advent13.hs
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+{-# LANGUAGE NegativeLiterals #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.Text (Text)
+import qualified Data.Text as T
+import qualified Data.Text.IO as TIO
+
+import Text.Megaparsec
+import qualified Text.Megaparsec.Lexer as L
+import Text.Megaparsec.Text (Parser)
+
+import qualified Control.Applicative as CA
+
+type ScannerDef = (Integer, Integer)
+type Scanner = Integer -> Integer
+
+
+main :: IO ()
+main = do 
+        text <- TIO.readFile "data/advent13.txt"
+        let scannerDefs = successfulParse text
+        print $ part1 scannerDefs
+        print $ part2 scannerDefs
+
+
+part1 :: [ScannerDef] -> Integer
+part1 = sum . map (uncurry (*)) . filter (\(d, r) -> scanner d r 0 == 0)
+
+
+part2 :: [ScannerDef] -> Integer
+part2 scannerDefs = head $ filter (canPass scanners) [0..]
+    where scanners = scanify scannerDefs
+
+
+scanify :: [ScannerDef] -> [Scanner]
+scanify = map (uncurry scanner)
+
+canPass :: [Scanner] -> Integer -> Bool
+canPass scannersF t = all (\s -> s t /= 0) scannersF
+
+
+scanner :: Integer -> Integer -> Integer -> Integer
+scanner depth range t = 
+    let t' = (t + depth) `mod` ((range - 1) * 2)
+    in if t' < range
+       then t' 
+       else range - t' - 1 -- t' + (t' - range + 1) * -2
+
+
+sc :: Parser ()
+sc = L.space (skipSome spaceChar) CA.empty CA.empty
+
+lexeme  = L.lexeme sc
+integer = lexeme L.integer
+symb = L.symbol sc
+
+scannersP = many scannerP
+
+scannerP = (,) <$> integer <*> (symb ":" *> integer)
+
+successfulParse :: Text -> [ScannerDef]
+successfulParse input = 
+        case parse scannersP "input" input of
+                Left  err   -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
+                Right scanners -> scanners     
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