Problem：

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:

 -

 -

 -

 - 

Solution:

理解格雷码和二进制的转换关系这题就很简单了。

格雷码的特点在于相邻两个数字仅有一位不同。题中给出的示例是【00,01,11,10】，原题提示中也说到格雷码的顺序可能不止一种，如【00,10,11,01】亦可，只需满足相邻两数只有一位不同这一条件。

按题示序列规则，对二进制数进行右移运算和异或运算可以得出相应格雷码，如：

// i ^(i>>1)

()^→()

()^→()

()^→()

()^→()

AC Code(C++):

 class Solution {

 public:

     vector<int> grayCode(int n) {

         vector<int> seq;

         for(int i=;i<(<<n);i++){

             seq.push_back(i^(i>>));

         }

         return seq;

     }

 };