Merge pull request #3 from aki1221/GH-1

leet code 941 solution

leet_941.rb

@@ -0,0 +1,22 @@
+# https://leetcode.com/problems/valid-mountain-array/
+# Runtime: 52 ms, faster than 73.08% of ruby online submissions for valid-mountain-array.
+
+def valid_mountain_array(a)
+  l = a.length
+  if l < 3
+    return false
+  else
+    l=l
+    i=0
+    while(i+1<l && a[i] < a[i+1])
+     i+=1
+    end
+   if i.eql?(0) || i.eql?(l-1)
+     return false
+   end
+   while(i+1<l && a[i+1] < a[i])    
+     i+=1
+   end
+  end
+  return i.eql?(l-1)
+end