Le blog de Siyao

Why coding algorithms

2018-12-09T00:00:00-05:00

Algorithm is fundamental of computer science, though it is not directly demanded in daily work. Continuing learning and solving algorithm problems makes me constantly aware of how many difficult problems exist in computer science area, and how tiny I am in computer science field. That is a big getaway for me, as CSer and tech worker, from the hype of all various of technologies, from up-and-down bubbled tech stock price, and from lucrative compensation TC numbers. It remindes me how I started CS track, and how I learned CS, and how I struggled with CS. I like the feeling of appreciation among all challenging problems in CS theories.

Keep coding, keep learning.

SL.

Why coding algorithms was originally published by Siyao at Le blog de Siyao on December 09, 2018.

Independent Film: Tiger Eyes

2015-02-13T00:00:00-05:00

I love independent film.

Independent film is a kind of art, conveying intensive view of everything, while movies in theater is better for killing time.

pic from: http://www.csmonitor.com

Independent Film: Tiger Eyes was originally published by Siyao at Le blog de Siyao on February 13, 2015.

Overview of Angular JS

2015-02-09T00:00:00-05:00

#AngularJS?

Based on JavaScript, like PHP and other script languages, can do (virtually) everything at client side.

#Build Website by AngularJS? It is enough!

##How to deploy on server?

I was confused by this. Because you can click the html file and see the website, but how to access via Internet? Apache server! It holds files on server, very powerful!

##Sometimes need more

###Bower? Package denpendecy manager. Declare lib dependency in bower.json, and type “bower install” to download all js libs. It is like maven in Java, but more light-weighted.

###Grunt? Make script alive. It is “task runner”, doing automations. Simply, it is something outside AngularJS, and do testing, minimize js libs into 1 file, and also can start up a server for scripts. Then you don’t need Apache server any more.

#Enough by AngularJS? Not really! Script is mainly used for loading views and handling some logic by controller in the middle. But cannot take heavy tasks. So we need more! MEAN.JS is a solution! MongoDB, Express, AngularJS, NodeJS. We have focused on AngularJS on client side. Now, M+E+N build the back-end server. Express is the web framework building on NodeJS, making it easier to handle web events. And NodeJS is server-side JS which connects MongoDB. MongoDB creates/ updates/ inserts/ deletes/ queries Json-format data.

#General View of App Generally, back-end server runs REST service. And front-end AngularJS makes request to REST server, and gets data to update views. That is very similar to mobile App dev. Client side code is equivalent to mobile app code, which both make request to REST server (or other ways) to obtain required data to update views. But mobile app is more complicated as it has cache mechanism so that can run offline as well.

Some traditional web apps, according to my understanding, are more rigid for front/back-end binding. Like structs in J2EE, the web app runs on the web container, and catch URL request, then route it to some functions to do logics, and then render the view page (asp for example), injecting data and loading the view. The workflow is like: request ->(struts) back-end -> view with data. And the web work with REST service is like: request -> view without data(js/php) -> back-end(restful) -> view with data.

#Conclusion Should learn more!

Overview of Angular JS was originally published by Siyao at Le blog de Siyao on February 09, 2015.

Summary of Binary Tree Traversal

2015-01-28T00:00:00-05:00

I guess some people think that iterative version of tree traversal is tedious to implement. But I found a very interesting fact that could make it as simple as recursive version.

As a reminder, for recursive version of pre/in/post-order traversal, the only difference is the order of following three lines:

dfs(root.left);//rec-l1
print(root);//rec-l2
dfs(root.right);//rec-;3

Similarly, if we take advantage of dummy node, for iterative version, the only difference is also the order of three lines:

if(node.right!=null) stack.push(node.right);//iter-l1
stack.push(node); stack.push(null);//iter-l2
if(node.left!=null) stack.push(node.left);//iter-l3

You may have noticed that the above two clips of code both represent the inorder traversal. And if we follow the order of rec-l1, rec-l3, rec-l2 or iter-l2, iter-l1, iter-l3, then we could get the postorder traversal. The source code of iterative version is shown at:

Most interestingly, there is another property of postorder traversal. Suppose we have a tree T, and the mirror tree of T is T’. Then postorder(T).reverse() equals to preorder(T’). So, if we use two stacks, then we could solve the postorder problem more simpler! The source code is shown at:

postorder (two stacks)

Both 2 solutions for postorder traversal can be extended to solve the n-ary tree postorder traversal (which could be a follow-up in a interview!).

Summary of Binary Tree Traversal was originally published by Siyao at Le blog de Siyao on January 28, 2015.

iOS: 3 Ways to Create Views

2015-01-25T00:00:00-05:00

I just started to learn iOS dev. And I discovered 3 ways to organized and navigate views for iOS.

Storyboard
Xib
By programming code

I initially followed the tutorial provided by Apple, and it instructs to use storyboard to organize views, which is visualizable. And later on I found some other projects are using xib. Some articles summrized the pro/con of those two methods. But the most interesting/technical way is to write view by code. I dig into the source code of Anypic, and fonud that programming the view is more universal though less visualizable. But I still love the third one. I found an article the compares the 3 methods for reference.

iOS: 3 Ways to Create Views was originally published by Siyao at Le blog de Siyao on January 25, 2015.

Autumn of NYC Comes Quietly

2014-10-12T00:00:00-04:00

Bad cough, homeworks, interview, midterm, but the only thing I didn’t care is the autumn that I have missed for 4 years. Very similar to the aumtumn of Beijing, it is cool, it is dry, and it is landscape.

View Outside My Window

Autumn of NYC Comes Quietly was originally published by Siyao at Le blog de Siyao on October 12, 2014.

Night of New York City

2014-09-22T00:00:00-04:00

Sometimes, I really want to photograph something that cannot feel by words. I was taking this photo on campus. Columbia University is 4 floor higher than the street height, so that you can oversee Broadway on campus.

Night View of Broadway Standing on Campus.

Night of New York City was originally published by Siyao at Le blog de Siyao on September 22, 2014.

My Personal Website is Now Open

2014-08-08T00:00:00-04:00

Why Blog

Finally I decide to open my own customized personal blog website. The reason why I open such a nonesense is not because I want to say something powerfully, rather more, I just want to own my own website, as if the whole designing and coding is all by myself. Unfortunately, not. Nevertheless, I have the superuser root of the website. I could modify codes, adding new features into the site. It seems I have things to do when I feel bored at the mid-night.

How it Works

Actually, creating such a website is a little bit technical. At first, I thought website should be something like J2EE or .Net, at least involving database. I thought that a website with pure html is just document instead of website. But actually, static website, namely html, could be more powerful than what I have thought. Some tools like jekyll can automatically generate static website pages according to your posts. I am not trying to make you understand how this site works. I just want to let you know how powerful a static website could be.

Although pure html pages do not involve with database, it does not mean that the website cannot have fancy features that requires persistent data. We can add some third-part JS plug-in into our html pages. Actually, the plug-in providers have database to store and load your data. I use a fancy plug-in DISQUS that allows readers to add comments via facebook, twitter etc. The comments are not stored in my website, instead, it stores at DISQUS server. Comments data will be loaded everytime I call the plugin. So, static website is powerful!

If you are interested in creating your own blog at Github Pages, here is a short guide. You may use Jekyll to generate html pages from plain text (actually markdown format). You can use some fancy Jekyll themes contributed by awsome desingers. So the whole technical things are Github + Jekyll + Markdown. Buildnig your own blog is simple!

And, I am trying to persuade William Wang to use Jekyll or other generators to build his personal website at UMich, which looks like fancier. :P

My Personal Website is Now Open was originally published by Siyao at Le blog de Siyao on August 08, 2014.

Hack Online Flappy Bird

2013-01-01T00:00:00-05:00

This is my first original video

I am using this video to test video-embeding function.

This is my first orignial video in my life. I happened to play the multi-player version of Flappy Bird online, a very popular mobile game for a time. I saw the source code and found that this game is purely made by javascript! How amazing! For the sake of respect, I hacked the code and gave the bird super power. I feel happy to see all of other birds fall down time after time, while my bird is free to cross the wall. I uploaded the video to BILIBILI and has been watched by thousands of people, and got nearly a hundred comments. That’s fun!

Hack Online Flappy Bird was originally published by Siyao at Le blog de Siyao on January 01, 2013.