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:

class Solution {
public:
    vector<int> grayCode(int n) {
    vector<int>result;
    if(0==n){result.push_back(0);return result;}
    if(1==n)
    {
        result.push_back(0);
        result.push_back(1);
        return result;
    }
    vector<int> temp=grayCode(n-1);
    vector<int> result2;
    for(int i=0;i<temp.size();i++)
    {
        result.push_back(temp[i]);
        result2.push_back(temp[temp.size()-1-i]+pow(2.0,n-1));
    }
    for(int i=0;i<result2.size();i++)
        result.push_back(result2[i]);
    return result;    
    }
};