Hello Thanks for all the help!
I only have a couple of questions. On Thu, Dec 3, 2009 at 03:45, Daniel Fischer <[email protected]> wrote: > Am Mittwoch 02 Dezember 2009 22:44:01 schrieb Don Stewart: >> aditya87: >> > Hi, >> > >> > I am trying to solve this problem: https://www.spoj.pl/problems/LASTDIG/ >> > It is very simple. Given a and b, return the last digit of a^b. b >> > could be large, so I used logarithmic exponentiation and > > Just to mention it, you can do something much much faster for this problem. > Something in the microsecond range (if IO is fast enough, millisecond > otherwise). > I guess you mean that we can find the cycle that the last digits follow while multiplying repeatedly by a, and then use that. I'll try that next in Haskell! >> {-# LANGUAGE BangPatterns #-} >> >> lastdigit :: Int -> Int -> Int -> Int >> lastdigit 0 0 _ = 1 >> lastdigit a b !c | even b = lastdigit ( (a*a) `rem` 10 ) (b `quot` >> 2) c >> >> | b == 1 = (a*c) `rem` 10 > > However, > > | otherwise = lastdigit ( (a*a) `rem` 10 ) (b `quot` 2) (a*c) This bang pattern (!c) is giving me pattern match errors. Is its only effect evaluating c instead of plain substitution? -- Aditya Manthramurthy _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
