【LeetCode】Gray Code

题目描述：

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 - 001 - 111 - 310 - 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.

关于格雷码的说明：维基百科：格雷码

用镜射排列的方法。

vector<int> grayCode(int n) {vector<int> code;code.push_back(0);for (int i = 1; i <= n; i++){int N = code.size() - 1;int inc = 1 << i - 1;for (int j = N; j >= 0; j--)code.push_back(code[j] + inc);}return code;}