89. Gray Code

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Problem

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].

Code

class Solution {
    public List<Integer> grayCode(int n) {
        // 格雷码（循环二进制单位距离码）是任意两个相邻数的代码只有一位二进制数不同的编码
        List<Integer> res = new ArrayList<>();
        for(int i = 0; i < (1 << n); i++){
            res.add(i ^ (i >> 1));
        }

        return res;
    }
}