[LeetCode] Problem 89 - Gray Code

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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

No.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

No.2

Input: 0

Output: [0]

Explanation: We define the gray code sequence to begin with 0. A gray code sequence of n has size = 2^n, which for n = 0 the size is 2^0 = 1. Therefore, for n = 0 the gray code sequence is [0].

Code

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public List<Integer> grayCode(int n) {
    List<Integer> result = new ArrayList<>();

    for (int i = 0; i < (1 << n); i++)
        result.add((i >> 1) ^ i);

    return result;
}