89. Gray Code java solutions

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.

 1 public class Solution {
 2     public List<Integer> grayCode(int n) {
 3         List<Integer> ans = new ArrayList<Integer>();
 4         int len = (int)Math.pow(2,n);
 5         for(int i = 0; i< len ;i++){
 6             ans.add(i^(i>>1));// 按照数学公式的解法。G(N) = (B(n)/2) XOR B(n).
 7         }
 8         return ans;
 9     }
10 }

二进制数转格雷码

（假设以二进制为0的值做为格雷码的0）

G：格雷码 B：二进制码

G(N) = (B(n)/2) XOR B(n).

以三位为例:

000^000-->000

001^000-->001

010^001-->011

011^001-->010

100^010-->110

101^010-->111

110^011-->101

111^011-->100

解法二： 可用递归。以后在总结。

参考帖子：

http://blog.csdn.net/makuiyu/article/details/44926463

http://www.cnblogs.com/peihao/p/5269151.html （第二个帖子描述的还是不够清晰一些）

89. Gray Code java solutions

原文：http://www.cnblogs.com/guoguolan/p/5619709.html