```
public class Solution
extends Object
```
89 - Gray Code\. Medium An **n-bit gray code sequence** is a sequence of 2ⁿ integers where: * Every integer is in the **inclusive** range [0, 2ⁿ - 1], * 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]. - 00 and 01 differ by one bit - 01 and 11 differ by one bit - 11 and 10 differ by one bit - 10 and 00 differ by one bit [0,2,3,1] is also a valid gray code sequence, whose binary representation is [00,10,11,01]. - 00 and 10 differ by one bit - 10 and 11 differ by one bit - 11 and 01 differ by one bit - 01 and 00 differ by one bit **Example 2:** **Input:** n = 1 **Output:** [0,1] **Constraints:** * `1 <= n <= 16`

public List<Integer> grayCode(int n)

Class Solution