This prompt means: given an input of "0", your program generated and output of "", but the expected answer is "".
Therefore, the program is incorrect.
Yes, it is definitely right. There is always
2^n elements in result list.
n=0, there should be
2^n = 2^0 = 1 element. You can consider it as an edge case.
The reason why the output is  for input  is that a gray code sequence must begin with 0 according to the problem statement. Even input is  meaning the number of bits is zero, the output starts with zero. Since number of bits is 0, we do not add anything to gray code sequence, so output becomes .
Yeah, I don't agree either. If n=0, then, since "...n representing the total number of bits in the code..", every element of the gray code sequence needs to have length 0. So yes, even though the question says every gray code starts with zero, the gray code for n=0, meaning , does trivially start with zero since it has no length. That test case should be changed.
Looks like your connection to LeetCode Discuss was lost, please wait while we try to reconnect.