題目描述

The gray code（格雷碼） 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.

什麽是格雷碼？

　　格雷碼是一種循環二進制單位距離碼，主要特點是兩個相鄰數的代碼只有一位二進制數不同的編碼，格雷碼的處理主要是位操作 Bit Operation

解題思路：

• 二進制碼->格雷碼（編碼）：從最右邊一位起，依次將每一位與左邊一位異或（XOR），作為對應格雷碼該位的值，最左邊一位不變（相當於左邊是0）；

• 格雷碼->二進制碼（解碼）：

　　從左邊第二位起，將每位與左邊一位解碼後的值異或，作為該位解碼後的值。

AC代碼：

class Solution {
public:
    vector<int> grayCode(int n) {
        vector
 
<int> res;
        for(int i=0;i<pow(2,n);i++){
            res.push_back((i>>1)^i);
        }
        return res;
    }
};

gray-code （格雷碼）