89 - Gray Code\.

Medium

An n-bit gray code sequence is a sequence of <code>2ⁿ</code> integers where:

• Every integer is in the inclusive range <code>0, 2ⁿ - 1</code>,

• The first integer is 0,

• An integer appears no more than once in the sequence,

• The binary representation of every pair of adjacent integers differs by exactly one bit , and

• The binary representation of the first and last integers differs by exactly one bit.

Given an integer n, return any valid n-bit gray code sequence.

Example 1:

Input: n = 2

Output: 0,1,3,2

Explanation: The binary representation of 0,1,3,2 is 00,01,11,10. - 0<ins>0</ins> and 0<ins>1</ins> differ by one bit - <ins>0</ins>1 and <ins>1</ins>1 differ by one bit - 1<ins>1</ins> and 1<ins>0</ins> differ by one bit - <ins>1</ins>0 and <ins>0</ins>0 differ by one bit 0,2,3,1 is also a valid gray code sequence, whose binary representation is 00,10,11,01. - <ins>0</ins>0 and <ins>1</ins>0 differ by one bit - 1<ins>0</ins> and 1<ins>1</ins> differ by one bit - <ins>1</ins>1 and <ins>0</ins>1 differ by one bit - 0<ins>1</ins> and 0<ins>0</ins> differ by one bit

Example 2:

Input: n = 1

Output: 0,1

Constraints:

• 1 <= n <= 16