Given 2 integers n and start. Your task is return any permutation p of (0,1,2.....,2^n -1) such that :
p[0] = startp[i]andp[i+1]differ by only one bit in their binary representation.p[0]andp[2^n -1]must also differ by only one bit in their binary representation.
Example 1:
Input: n = 2, start = 3 Output: [3,2,0,1] Explanation: The binary representation of the permutation is (11,10,00,01). All the adjacent element differ by one bit. Another valid permutation is [3,1,0,2]
Example 2:
Input: n = 3, start = 2 Output: [2,6,7,5,4,0,1,3] Explanation: The binary representation of the permutation is (010,110,111,101,100,000,001,011).
Constraints:
1 <= n <= 160 <= start < 2 ^ n