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 - 001 - 111 - 310 - 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.

Solution:

I have learned about gray code in class before ,but I totally forget about it. then use some small case to find the relationship between them. the job will be done.

class Solution {public:    vector<int> grayCode(int n) {        // Start typing your C/C++ solution below// DO NOT write int main() functionvector<int> res;        if(n ==0){            res.push_back(0);            return res;        }else{res = grayCode(n-1);int pos = (1<<(n-1)) - 1;int cur = 1 + pos;for(int i = pos; i >= 0; --i){res.push_back(cur | res[i]);}return res;}}};