[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.

 1 class Solution
 2 {
 3 public:
 4     /*
 5      * for reference: http://en.wikipedia.org/wiki/Gray_code.
 6      */
 7     vector<int> grayCode(int n)
 8     {
 9         vector<int> ret;
10         int size = 1 << n;
11         for(int i = 0; i < size; ++i)
12             ret.push_back((i >> 1)^i);
13         return ret;
14     }
15 };