Here's a (non-pretty) version in haskell:
-- begin program --
-- Written by B. Donlan
permute :: [a] -> [[a]]
permute [] = [[]]
permute [x] = [[x]]
permute l = concat $ map pick [0..(length l) - 1]
where pick n = map ((l !! n):) $ permute (take n l ++ drop (n + 1) l)
main = do
putStrLn $ show $ permute [1 .. 10]
-- end program --
Note: the $ is a lot like the | in the unix shell, it's for making
pipelines of functions.
It has a pretty good runtime when compiled with the glasgow haskell
compiler, with -O3:
% time ./permute > perm2
./permute > perm2 50.01s user 0.91s system 94% cpu 53.731 total
That's really good runtime considering it produced 3628800 permutations!
perm2 is around 80MB.
Can anyone guess what the memory consumption was?
--
Colvard's Unconscionable Commentary:
This is especially true when dealing with someone you're attracted to.
Grelb's Commentary:
Likelihoods, however, are 90% against you.
-
GPG Fingerprint: E3CD FDAB 82C4 14FD 7B57 430B 770E 0EAF FB53 12C2
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