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.

Solution:

Code:

<span style="font-size:14px;">class Solution {
public:
    vector<int> grayCode(int n) {
        vector<int> result;
        result.push_back(0);
        if (n == 0) return result;
        result.push_back(1);
        if (n == 1) return result;
        int index = 2;
        int bit = 1<<1;
        while (index <= n) {
            int length = result.size();
            for (int i = length-1; i >= 0; i--) {
                result.push_back(result[i] | bit);
            }
            bit = bit<<1;
            index++;
        }
        return result;
    }
};</span>