leetcode_Gray Code

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.

For now, the judge is able to judge based on one instance of gray code sequence. Sorry about that.

思路：

1.n位格雷码对应有1<<n个数

2.每个数字对应的格雷码的对应的计算公式为：i^(i/2)

代码：

public List<Integer> grayCode(int n) {        List<Integer>list=new ArrayList<Integer>();        if(n<0)            return list;        n=1<<n;        for(int i=0;i<n;i++)            list.add((i^(i/2)));        return list;    }