【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) {
        int size = 1 << n;
        vector<int> ret;
        ret.resize(size);
        for (int i = 0; i < size; i++){
            ret[i] = i ^ i>>1;
        }
        return ret;
    }
};

用公式吧，多快好省啊...

gray(i) = i ^ (i >> 1)