leetcode 89:Gray Code

转：https://github.com/soulmachine/leetcode

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.

格雷码(Gray Code) 的定义请参考https://en.wikipedia.org/wiki/Gray_code

这题要求生成n 比特的所有格雷码。

方法1，最简单的方法，利用数学公式，对从0  2^n - 1) 的所有整数，转化为格雷码。

方法2，n 比特的格雷码，可以递归地从n -1 比特的格雷码生成。