Day 5: Cafeteria

Megathread guidelines

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FAQ

  • Amy@piefed.blahaj.zoneEnglish
    3·
    10 hours ago

    Haskell

    IntSet was the wrong first choice for part 2 :3

    import Control.Arrow  
import Data.Foldable  
import Data.Ix  

readInput :: [Char] -> ([(Int, Int)], [Int])  
readInput =  
  (map readRange *** (map read . tail))  
    . break (== "")  
    . lines  
  where  
    readRange = (read *** (read . tail)) . break (== '-')  

part1 (ranges, ids) = length $ filter (\id -> any (`inRange` id) ranges) ids  

part2 (ranges, _) = sum $ map rangeSize $ foldl' addRange [] ranges  
  where  
    addRange [] x = [x]  
    addRange (r : rs) x  
      | touching r x = addRange rs $ merge r x  
      | otherwise = r : addRange rs x  
    touching (a, b) (c, d) = not (b < c - 1 || a > d + 1)  
    merge (a, b) (c, d) = (min a c, max b d)  

main = do  
  input <- readInput <$> readFile "input05"  
  print $ part1 input  
  print $ part2 input