[LeetCode] 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.

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.

class Solution
{
public:
    /*
     * for reference: http://en.wikipedia.org/wiki/Gray_code.
     */
    vector<int> grayCode(int n)
    {
        vector<int> ret;
        int size = 1 << n;
        for(int i = 0; i < size; ++i)
            ret.push_back((i >> 1)^i);
        return ret;
    }
};