The gray code is a binary numeral system where two successive values differ in only one bit.
Given a non-negative integer n representing the total number of bits in the code, print the sequence of gray code. A gray code sequence must begin with 0.
Example 1:
Input: 2 Output: [0,1,3,2] Explanation: 00 - 0 01 - 1 11 - 3 10 - 2
For a given n, a gray code sequence may not be uniquely defined. For example, [0,2,3,1] is also a valid gray code sequence.
00 - 0 10 - 2 11 - 3 01 - 1 Example 2:
Input: 0 Output: [0] Explanation: We define the gray code sequence to begin with 0. A gray code sequence of n has size = 2n, which for n = 0 the size is 20 = 1. Therefore, for n = 0 the gray code sequence is [0].
My code:
class Solution:
'''
from up to down, then left to right
0 1 11 110
10 111
101
100
start: [0]
i = 0: [0, 1]
i = 1: [0, 1, 3, 2]
i = 2: [0, 1, 3, 2, 6, 7, 5, 4]
'''
def grayCode(self, n):
results = [0]
for i in range(n):
results += [x + pow(2, i) for x in reversed(results)]
return results