# 89. Gray Code (Medium)

https://leetcode.com/problems/gray-code/

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: ```
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 .```
```

## Solutions

``````class Solution {
public List<Integer> grayCode(int n) {
List<Integer> result = new ArrayList<>();
for (int i = 0; i <= ((1 << n) - 1); i++) {
result.add(i ^ (i >> 1));
}

return result;
}
}
``````