Gray Code | Leetcode

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.

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

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

Note:
For a given n, 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.

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Solution: Not a fun problem. See https://en.wikipedia.org/wiki/Gray_code.

public class Solution {
    private int binaryToGray(int n) {
        return (n >> 1) ^ n;
    }
    
    public List<Integer> grayCode(int n) {
        int max = (int) Math.pow(2, n);
        List<Integer> list = new ArrayList<>(max);
        for (int i = 0; i < max; i++) {
            list.add(binaryToGray(i));
        }
        return list;
    }
}