99 questions/Solutions/25
< 99 questions | Solutions
Jump to navigation
Jump to search
Generate a random permutation of the elements of a list.
rnd_permu xs = diff_select' (length xs) xs
Uses the solution for the previous problem. Choosing N distinct elements from a list of length N will yield a permutation.
Or we can generate the permutation recursively:
import System.Random (randomRIO)
rnd_permu :: [a] -> IO [a]
rnd_permu [] = return []
rnd_permu (x:xs) = do
rand <- randomRIO (0, (length xs))
rest <- rnd_permu xs
return $ let (ys,zs) = splitAt rand rest
in ys++(x:zs)