89. Gray Code #Medium

leetcode 89. Gray Code #Medium

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

题意：

根据所给数字n生成2^n个连续的格雷码

分析：

举例

n=1, [0, 1]

n=2, [00, 01, 11, 10]

n=3, [000, 001, 011, 010, 110, 111, 101, 100]

后一个序列的前半段就是前一个序列，后半段是前一个序列的每个数字左边补1，然后反向排列这些数字。根据此规律可求解

C++代码：

[code]class Solution {
public:
vector grayCode(int n) {
vector r1(1,0),r2;
if(n