From a9abc1da41b56edbed00081800382e854d6698d0 Mon Sep 17 00:00:00 2001 From: Joe Zhao Date: Tue, 31 Mar 2015 23:41:55 +0800 Subject: rename to H**, +31 +32 +33 +34 +35 +36 --- H23.hs | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) create mode 100644 H23.hs (limited to 'H23.hs') diff --git a/H23.hs b/H23.hs new file mode 100644 index 0000000..f85a87a --- /dev/null +++ b/H23.hs @@ -0,0 +1,21 @@ +import System.Random +import Data.List + +rnd_select :: [a] -> Int -> IO [a] +rnd_select _ 0 = return [] +rnd_select (x:xs) n = + do + r <- randomRIO (0, (length xs)) + if r < n + then do + rest <- rnd_select xs (n-1) + return (x : rest) + else rnd_select xs n + +rnd_select' xs n = do + gen <- getStdGen + return $ take n [ xs !! x | x <- randomRs (0, (length xs) - 1) gen] + +rnd_select'' :: Int -> [a] -> [a] +rnd_select'' n x = map (x!!) is + where is = take n . nub $ randomRs (0, length x - 1) (mkStdGen 100) -- cgit v1.2.3-70-g09d2