Gray Code

Question:

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.

Solution:

 1 class Solution {
 2 public:
 3     vector<int> grayCode(int n) {
 4     vector<int>result;
 5     if(0==n){result.push_back(0);return result;}
 6     if(1==n)
 7     {
 8         result.push_back(0);
 9         result.push_back(1);
10         return result;
11     }
12     vector<int> temp=grayCode(n-1);
13     vector<int> result2;
14     for(int i=0;i<temp.size();i++)
15     {
16         result.push_back(temp[i]);
17         result2.push_back(temp[temp.size()-1-i]+pow(2.0,n-1));
18     }
19     for(int i=0;i<result2.size();i++)
20         result.push_back(result2[i]);
21     return result;    
22     }
23 };

Gray Code

原文：http://www.cnblogs.com/riden/p/4631579.html