From 13c0046a6dbd41b15358e76856922144ac76e768 Mon Sep 17 00:00:00 2001
From: Joe Zhao <ztuowen@gmail.com>
Date: Sat, 4 Apr 2015 17:38:20 +0800
Subject: +46 +47 +48 +49 +50

---
 H49.hs | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 H49.hs

(limited to 'H49.hs')

diff --git a/H49.hs b/H49.hs
new file mode 100644
index 0000000..57f16b5
--- /dev/null
+++ b/H49.hs
@@ -0,0 +1,8 @@
+import Control.Monad (replicateM)
+
+gray = map construct . (flip replicateM) ['0','1']
+    where construct x = zipWith (\a b -> if a == b then '0' else '1') ('0':x) x
+
+gray' :: Integral a => a -> [String]
+gray' 0 = [""]
+gray' n = foldr (\s acc -> ("0" ++ s):("1" ++ s):acc) [] $ gray (n-1)
-- 
cgit v1.2.3-70-g09d2