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authorJulien Dessaux2024-12-16 22:26:23 +0100
committerJulien Dessaux2024-12-16 22:26:23 +0100
commit9ed8dc9af26b19716616246250553df3ffdf5d37 (patch)
tree4abf1dc0df1948af80f3afc9cd3e724501a7a487 /2024/13-Claw_Contraption/second.hs
parent2024-12 in haskell (diff)
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2024-13 in haskell
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+-- requires cabal install --lib megaparsec parser-combinators heap vector
+module Main (main) where
+
+import Control.Monad (void, when)
+import Data.Either
+import qualified Data.Matrix as MTX
+import Data.Ratio
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+
+type Pair = (Rational, Rational) -- X Y
+type Entry = (Pair, Pair, Pair) -- ButtonA ButtonB Prize
+type Input = [Entry]
+
+type Parser = Parsec Void String
+
+parseNumber :: Parser Rational
+parseNumber = fromInteger . read <$> some digitChar
+
+parseButton :: Parser Pair
+parseButton = (,) <$> (string "Button " *> letterChar *> string ": X+" *> parseNumber)
+ <*> (string ", Y+" *> parseNumber <* eol)
+
+parsePrize :: Parser Pair
+parsePrize = (,) <$> (string "Prize: X=" *> parseNumber)
+ <*> (string ", Y=" *> parseNumber <* eol)
+
+parseEntry :: Parser Entry
+parseEntry = (,,) <$> parseButton
+ <*> parseButton
+ <*> parsePrize
+
+parseInput' :: Parser Input
+parseInput' = some (parseEntry <* optional eol) <* eof
+
+parseInput :: String -> IO Input
+parseInput filename = do
+ input <- readFile filename
+ case runParser parseInput' filename input of
+ Left bundle -> error $ errorBundlePretty bundle
+ Right input' -> return input'
+
+-- ax + bx = c
+-- ay + by = d
+compute :: Input -> Rational
+compute = sum . map compute'
+ where
+ compute' ((ax, ay), (bx, by), (px, py)) = let (Right sol) = MTX.rref $ MTX.fromList 2 3 [ ax, bx, px + 10000000000000
+ , ay, by, py + 10000000000000 ]
+ x = sol MTX.! (1, 3)
+ y = sol MTX.! (2, 3)
+ in if (denominator x == 1 && denominator y == 1) then 3 * x + y else 0
+
+main :: IO ()
+main = do
+ input <- parseInput "input"
+ print $ compute input