LeetCode - Gray Code

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.

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