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.

思路：

在已有的数组中，增加一个最高位得到一个新数组，然后压入原数组，如此循环。

程序可以写的非常简洁。

当然有数学公式可以计算的，不过面试程序题，还是写个循环比较保险。

 

vector<int> grayCode(int n) 
	{
		vector<int> v(1);
		for (int i = 0; i < n; i++)
		{
			int h = v.size();
			for (int j = v.size() - 1; j >= 0 ; j--)
				v.push_back(h|v[j]);
		}
		return v;
	}