71 lines
2.6 KiB
Haskell
71 lines
2.6 KiB
Haskell
-- requires cabal install --lib megaparsec parser-combinators
|
|
module Main (main) where
|
|
|
|
import Control.Applicative.Permutations
|
|
import Control.Monad (void, when)
|
|
import Data.Char qualified as C
|
|
import Data.Either
|
|
import Data.List qualified as L
|
|
import Data.Map qualified as M
|
|
import Data.Maybe
|
|
import Data.Set qualified as S
|
|
import Data.Void (Void)
|
|
import Text.Megaparsec
|
|
import Text.Megaparsec.Char
|
|
|
|
exampleExpectedOutput = 46
|
|
|
|
data Range = Range Int Int deriving Show -- start range
|
|
data Map = Map Int Range deriving Show -- destination range
|
|
data Mapping = Mapping String String [Map] deriving Show -- sourceStr destStr
|
|
data Input = Input [Range] [Mapping] deriving Show -- seeds mappings
|
|
|
|
type Parser = Parsec Void String
|
|
|
|
parseNumber :: Parser Int
|
|
parseNumber = read <$> some digitChar <* many (char ' ')
|
|
|
|
parseRange :: Parser Range
|
|
parseRange = Range <$> parseNumber
|
|
<*> parseNumber
|
|
|
|
parseMap :: Parser Map
|
|
parseMap = Map <$> parseNumber
|
|
<*> parseRange <* eol
|
|
|
|
parseMapping :: Parser Mapping
|
|
parseMapping = Mapping <$> (some letterChar <* string "-to-")
|
|
<*> (some letterChar <* string " map:" <* eol)
|
|
<*> some parseMap <* optional eol
|
|
|
|
parseInput' :: Parser Input
|
|
parseInput' = Input <$> (string "seeds: " *> some parseRange <* some eol)
|
|
<*> some parseMapping <* 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'
|
|
|
|
step :: [Map] -> Range -> [Range]
|
|
step [] n = [n]
|
|
step (Map dest (Range src range):ms) r@(Range n l) | n+l<=src || n>=src+range = step ms r
|
|
| n>=src && n+l<=src+range = [Range (n-src+dest) l]
|
|
| n>=src = Range (n-src+dest) (range+src-n) : step ms (Range (src+range) (l-range-src+n))
|
|
| otherwise = Range dest (l-src+n) : step ms (Range n (src-n))
|
|
|
|
stepMapping :: [Range] -> Mapping -> [Range]
|
|
stepMapping ranges (Mapping _ _ ms) = concatMap (step ms) ranges
|
|
|
|
compute :: Input -> Int
|
|
compute (Input ranges mappings) = minimum $ map (\(Range start _) -> start) $ L.foldl' stepMapping ranges mappings
|
|
|
|
main :: IO ()
|
|
main = do
|
|
example <- parseInput "example"
|
|
let exampleOutput = compute example
|
|
when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
|
|
input <- parseInput "input"
|
|
print $ compute input
|