Leetcode: 89. Gray Code

Description

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.

Example

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.

思路

• 图片截自LeetCode89:Gray Code

代码

class Solution {
public:
    vector<int> grayCode(int n) {
        vector<int> res(1);
        for(int i = 0; i < n; ++i){
            for(int j = res.size() - 1; j >= 0; --j)
                res.push_back((1 << i) + res[j]);
        }
        
        return res;
    }
};