On Wed, Oct 15, 2008 at 5:44 PM, leledumbo <[EMAIL PROTECTED]> wrote: > > module Main where > > import Data.List > > -- quicksort of any list > qsort [] = [] > qsort (x:xs) = qsort(filter(<x) xs) ++ [x] ++ qsort(filter(>=x) xs) > > -- optimized quicksort, uses middle element as pivot > qsortOpt [] = [] > qsortOpt x = qsortOpt less ++ [pivot] ++ qsortOpt greater > where > pivot = x !! ((length x) `div` 2) > less = filter (<pivot) (delete pivot x) > greater = filter (>=pivot) (delete pivot x) > > main = do > putStr "Enter a list: " > l <- readLn > print (qsortOpt l) > -- end of code
I'm curious as to why taking the pivot from the middle is an 'optimized' version. For this to be true you must be making some assumptions about the contents of the list. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
