Leetcode OJ: 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

这题关键问题是什么是Gray code？

大家百科一下大概就知道什么是Gray code了，再多几个n的样例也能推出通式来，通过数字逻辑那一套。

不过有现成就直接用吧，二进制转Gray code的通式就是G(N) = (B(n)/2) XOR B(n)

代码如下：

 1 class Solution {
 2 public:
 3     vector<int> grayCode(int n) {
 4         int size = 1 << n;
 5         vector<int> ret;
 6         for (int i = 0; i < size; ++i) {
 7             ret.push_back((i >> 1) ^ i);
 8         }
 9         return ret;
10     }
11 };