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关于JavaScript

• Node.JS: server
• AngularJS: 前端（Google）
• jQuery: JS库
• Bootstrap: （Twitter）CSS库+blueprint样式的布局+基于JQuery的插件
• socket.io: 不同浏览器和移动设备上实现web 应用
• Express: 輕量靈活的node.js Web應用框架 http://xvfeng.me/posts/understanding-expressjs/
• Mongoose: 是基于node-mongodb-native开发的MongoDB nodejs驱动，可以在异步的环境下执行。
• Bower: twitter的包管理工具 http://chuo.me/2013/02/twitter-bower.html
• Grunt: 是一个Javascript Task Runner（Javascript任务运行器），其基于NodeJS，可用于自动化构建、测试、生成文档的项目管理工具。 http://www.cnblogs.com/justany/archive/2013/04/16/3024106.html

AngularJS基于GoogleV8 JavaScript 引擎，将JavaScript转成native machine code prior to execution

MEAN 框架

AngularJS, NodeJs, ExpressJs with MongoDB as backend.  Together these are popularly referred as MEAN stack technologies.

• MongoDB - NoSQL Database .Written in C++, MongoDB features: JSON-style documents with dynamic schemas and Full Indexing support.
• NodeJS - Core -
• ExpressJS - Web app framework - Express is a minimal and flexible node.js web application framework, providing a robust set of features for building hybrid web applications.
• AngularJS - JS MVC - AngularJS is a client-side JavaScript framework , maintained by Google, that assists with running single-page applications.

第六周主题：数字 之 GrayCode in LeetCode (in java)

题目：

http://oj.leetcode.com/problems/gray-code/


要求：


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.




解答：

画画就出来了。为了好分析，我们看n=4的情况，那么一共有2^4=16种codes


 
 


  
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
 

  
1
  
1
  
0
  
0
 

  
1
  
1
  
0
  
1
 

  
1
  
1
  
1
  
1
 

  
1
  
1
  
1
  
0
 

  
1
  
0
  
1
  
0
 

  
1
  
0
  
1
  
1
 

  
1
  
0
  
0
  
1
 

  
1
  
0
  
0
  
0
 

规律：

（1）第一列对半分成up 和down 部分， up都是0，down都是1；

（2）从二列开始，在前一列子列的基础上，再对半细分成up和down部分，如果在第一列的down部分，则需要把01序列倒过来。

References:

[1] 代码在

https://github.com/RockyNiu/LeetCode/blob/master/src/leetcode/java/GrayCode.java