[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> res;
res.push_back(0);
if(n<1)//input:0,expected output:[0]
return res;
int index,diffValue;
for(int i=0;i<n;i++){
diffValue = (1<<i);
index = res.size();
while(index){
index--;
res.push_back(res[index]+diffValue);

}//end while

}//end for

return res;

}
};