[leetcode] Gray Code

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.

 

二进制转格雷码： 
从左边第二位起，将每位与左边一位的值异或，作为该位转码后的值（最左边一位依然不变）。 

格雷码转二进制：
从左边第二位起，将每位与左边一位解码后的值异或，作为该位解码后的值（最左边一位依然不变）。

 

class Solution
{
public:
  vector<int> grayCode(int n)
  {
    int size = 1 << n;
    vector<int> ret(size);

    for(int i=0; i<size; i++)
      ret[i] = i ^ (i >> 1);

    return ret;
  } 
};