Gray_Code.cpp

/*
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

 */
class Solution {
public:
    vector<int> grayCode(int n) {
        vector<int> result;
        result.push_back(0);

        int k = 0; //index
        int bit = 1;
        while (result.size() < (1<<n)) {
            result.push_back(result[k] + bit);
            k--;
            if (k < 0) {
                k = result.size() - 1;
                bit *= 2;
            }
        }

        return result;
    }
};