LeetCode--Gray Code

格雷码的定义

第二次写的，参考别人。代码写的很简洁

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