leetcode Gray Code 格雷码

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.

// 把binary code直接转为gray code：
// Binary Code ：1011 要转换成Gray Code
// 1011 = 1（照写第一位）, 1(第一位与第二位异或 1^0 = 1), 1(第二位异或第三位， 0^1=1), 0 (1^1 =0) = 1110
// 其实就等于 (1011 >> 1) ^ 1011 = 1110
class Solution {
public:
vector<int> grayCode(int n) {
vector<int> res;
for(int i = 0;i<(1<<n);i++) {
res.push_back((i>>1)^i);
}
return res;
}
};