drink.hs.txt

Ulm大学2003-2004年竞赛题

-- Problem   Drink, on Ice
-- Algorithm Thermodynamics
-- Runtime   O(1)
-- Author    Walter Guttmann
-- Date      04.05.2003

import Numeric;

main :: IO ()
main =
  do input <- readFile "drink.in"
     mapM_ solve $ cases $ map read $ words input

cases :: [Double] -> [(Double,Double,Double,Double)]
cases (0.0:0.0:0.0:0.0:_) = []
cases (mw:mi:tw:ti:xs) = (mw,mi,tw,ti) : cases xs

solve :: (Double,Double,Double,Double) -> IO ()
solve (mw,mi,tw,ti) = putStrLn $ format (m-mw_n) " g of ice and " ++ format mw_n " g of water at " ++ format t_n " C"
  where format = showFFloat (Just 1)
        (ci,cw,em,np) = (2.09,4.19,335.0,30.0)
        m = mw + mi
        e = mi * ci * (np + ti) + mw * (ci * np + em + cw * tw)
        (mw_n,t_n) =
          if e < m * ci * np then (0.0,e / (m * ci) - np)
          else if e < m * ci * np + m * em then ((e - m * ci * np) / em,0.0)
          else (m,(e - m * ci * np - m * em) / (m * cw))