Solution
from typing import List
class Solution:
def grayCode(self, n: int) -> List[int]:
return [i ^ (i >> 1) for i in range(1 << n)]
if __name__ == "__main__":
sol = Solution()
print(sol.grayCode(2)) # [0,1,3,2]
print(sol.grayCode(3)) # [0,1,3,2,6,7,5,4]