summaryrefslogtreecommitdiff
path: root/H23.hs
diff options
context:
space:
mode:
authorJoe Zhao <ztuowen@gmail.com>2015-03-31 23:41:55 +0800
committerJoe Zhao <ztuowen@gmail.com>2015-03-31 23:41:55 +0800
commita9abc1da41b56edbed00081800382e854d6698d0 (patch)
tree5265cc1c5296768438b67299afd59bcc57c58f0c /H23.hs
parent378f6303e8860b7bbca7dea787d584a6728cebf1 (diff)
downloadh99-a9abc1da41b56edbed00081800382e854d6698d0.tar.gz
h99-a9abc1da41b56edbed00081800382e854d6698d0.tar.bz2
h99-a9abc1da41b56edbed00081800382e854d6698d0.zip
rename to H**, +31 +32 +33 +34 +35 +36
Diffstat (limited to 'H23.hs')
-rw-r--r--H23.hs21
1 files changed, 21 insertions, 0 deletions
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)