GitHub Viewer
// Source : https://oj.leetcode.com/problems/gray-code/
// Author : Hao Chen
// Date : 2014-06-20
/**********************************************************************************
*
* 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.
*
**********************************************************************************/
#include
#include
#include
#include
#include
using namespace std;
/*
* I designed the following stupid algorithm base on the blow observation
*
* I noticed I can use a `mirror-like` binary tree to figure out the gray code.
*
* For example:
*
* 0
* __/ \__
* 0 1
* / \ / \
* 0 1 1 0
* So, the gray code as below: (top-down, from left to right)
*
* 0 0 0
* 0 0 1
* 0 1 1
* 0 1 0
*
* 0
* _____/ \_____
* 0 1
* __/ \__ __/ \__
* 0 1 1 0
* / \ / \ / \ / \
* 0 1 1 0 0 1 1 0
*
* So, the gray code as below:
*
* 0 0 0 0
* 0 0 0 1
* 0 0 1 1
* 0 0 1 0
* 0 1 1 0
* 0 1 1 1
* 0 1 0 1
* 0 1 0 0
*/
vector grayCode01(int n) {
vector v;
//n = 1