Gray Code

The gray code is a binary numeral system where two successive values differ in only one bit.

Given a non-negative integernrepresenting the total number of bits in the code, print the sequence of gray code. A gray code sequence must begin with 0.

For example, givenn= 2, return[0,1,3,2]. Its gray code sequence is:

00 - 0
01 - 1
11 - 3
10 - 2

Note:
For a givenn, a gray code sequence is not uniquely defined.

For example,[0,2,3,1]is also a valid gray code sequence according to the above definition.

For now, the judge is able to judge based on one instance of gray code sequence. Sorry about that.

Tips:

Bit Manipulation：非常巧妙，强行记一下吧。。

Code：

public class Solution {
    public List<Integer> grayCode(int n) {
        List<Integer> res = new ArrayList<>();
        res.add(0);
        for (int i = 0; i < n; i++) {
            int size = res.size();
            for (int j = size - 1; j >= 0; j--) {
                res.add(res.get(j) | 1 << i);
            }
        }
        return res;
    }
}