Added the solution for gray code problem

Look into this pr, this is my first pr, please guide me accordingly.

Author: 27Anurag

.DS_Store

@@ -0,0 +1,11 @@
+def gray(a):
+return ((a)^(a>>1))
+
+class Solution:
+ def grayCode(self, n: int) -> List[int]:
+ ans=[]
+ for i in range(pow(2,n)):
+ ans.append(gray(i))
+ return ans 
+
+