Here are some libraries that you may find helpful:

[arboreal.js][1], a &quot;micro-library for traversing and manipulating tree-like data structures&quot; in node.js and the browser.

[buckets][2], a &quot;complete, fully tested and documented data structure library&quot; that includes BSTs, a heap, and a bunch of other goodies.


  [1]: https://github.com/afiore/arboreal
  [2]: https://github.com/mauriciosantos/buckets/

Two libraries to add to the list are:

* [t.js](https://github.com/aaronj1335/t-js) - Seems to be good for traversal;
* [TreeModel](http://jnuno.com/tree-model-js/) - Manipulation and traversal.

_disclaimer: I built TreeModel_

Try the DOM

    var o = document.createElement( &#39;WHAT_YOU_WANT&#39; )
    // o.appendChild( ... )


Wish I&#39;d seen that solution before, because those libraries look helpful!  

Here is one I put together which is an alternative.  Meant for traversal, manipulation and loading of hierarchical tree structures from self referencing flat tables, not for balanced binary trees.

[DataStructures.Tree][1] and [related blog post][2]


  [1]: https://github.com/stephen-james/DataStructures.Tree
  [2]: http://stephenjamescode.blogspot.co.uk/2013/03/building-tree-in-javascript-to-convert.html

I am not sure what your needs are so this is a shot in the dark.
I normally use (for lightweight Javascript) an array of arrays, like this:

    node[i] = [parent, firstChild, secondChild, ... nthChild];


I wrote one simple data oriented tree library called [data-tree][1]. You can use this to create, traverse and search tree in BFS/DFS fashion. You can also import/export data from tree.  Checkout the detailed documentation at: http://cchandurkar.github.io/Data-Tree/

To use it in a node `npm install data-tree`


  [1]: https://github.com/cchandurkar/Data-Tree

When I load up a workspace (for Android Java development), Eclipse says in the status bar that it&#39;s updating indexes.  The Progress tab reports that it&#39;s hitting maven.org.

I read up on Maven - seems like a build manager.  What I don&#39;t understand is why my Android workspace needs it or why it&#39;s hitting the server in the cloud.  Do I need it?  If not, how do I safely remove it?

![enter image description here][1]


  [1]: http://i.stack.imgur.com/z6aXC.png

What is Eclipse doing when it says that it&#39;s updating indexes?

I have a base class MyBase that contains a pure virtual function: 

`void PrintStartMessage() = 0`


I want each derived class to call it in their constructor

then I put it in base class(`MyBase`) constructor

     class MyBase
     {
     public:
          
          virtual void PrintStartMessage() =0;
          MyBase()
          {
               PrintStartMessage();
          }
          
     };

     class Derived:public MyBase
     {     

     public:
          void  PrintStartMessage(){
               
          }
     };
     
    void main()
     {
          Derived derived;
     }

but I get a linker error.



     this is error message : 

     1&gt;------ Build started: Project: s1, Configuration: Debug Win32 ------
     1&gt;Compiling...
     1&gt;s1.cpp
     1&gt;Linking...
     1&gt;s1.obj : error LNK2019: unresolved external symbol &quot;public: virtual void __thiscall MyBase::PrintStartMessage(void)&quot; (?PrintStartMessage@MyBase@@UAEXXZ) referenced in function &quot;public: __thiscall MyBase::MyBase(void)&quot; (??0MyBase@@QAE@XZ)
     1&gt;C:\Users\Shmuelian\Documents\Visual Studio 2008\Projects\s1\Debug\s1.exe : fatal error LNK1120: 1 unresolved externals
     1&gt;s1 - 2 error(s), 0 warning(s)


I want force to all derived classes to... 
 
    A- implement it

    B- call it in their constructor 


How I must do it? 



call to pure virtual function from base class constructor

Are there good libraries for manipulating trees in javascript? Just to be clear, I am looking for tree as in data structure not display model.

What javascript tree data structures are available?

<p>Are there good libraries for manipulating trees in javascript? Just to be clear, I am looking for tree as in data structure not display model.</p>


I thought this would be a simple hack, but I&#39;ve now been searching for hours and can&#39;t seen to find the right search term. I want to have an ordinary multiple select box (`&lt;select multiple=&quot;multiple&quot;&gt;`) except I don&#39;t want the user to have to hold down the control key to make multiple selections. 

In other words, I want a left click to toggle the `&lt;option&gt;` element that&#39;s under the cursor without changing any of the others. In other other words, I want something that looks like a combo list box but behaves like a group of check boxes.

Can anybody suggest a simple way to do this in Javascript? Thanks.

How to avoid the need for ctrl-click in a multi-select box using Javascript?

Can someone help me with a javascript function that can highlight text on a web page.
And the requirement is to - highlight only once, not like highlight all occurrences of the text as we do in case of search.

How to highlight text using javascript

I have a string like this:

    abc=foo&amp;def=%5Basf%5D&amp;xyz=5

How can I convert it into a JavaScript object like this?

    {
      abc: &#39;foo&#39;,
      def: &#39;[asf]&#39;,
      xyz: 5
    }

How to convert URL parameters to a JavaScript object?

I&#39;m getting a JSON element and building a list from its items like this:

    getTitles: function(data) {
        data = data || {};
        var list = [];
        
        $.getJSON(
            &#39;/titles&#39;,
            data,
            function(data) {
                $.each(data.data, function(key, val) {
                    list.push(
                        &#39;&lt;li&gt;&lt;a href=&quot;&#39;+ val.href +&#39;&quot;&gt;&#39;+ val.title +&#39;&lt;/a&gt;&lt;span class=&quot;count&quot;&gt;&#39;+ val.count +&#39;&lt;/span&gt;&lt;/li&gt;&#39;
                    )
                });
                
                $(&#39;#title-items&#39;).html(list.join(&#39;&#39;));
            }
        );
    }

And I&#39;m binding click event for `a` elements like this:

    $(&#39;a&#39;).on(&#39;click&#39;, function(e) {
        alert(&#39;clicked&#39;);
        e.preventDefault();
    });

Old `a` elements shows alert but new ones follow URL. Event handler doesn&#39;t work for new ones. How can I solve this?

jQuery .on() method doesn&#39;t see new elements

I&#39;ve been looking over the JavaScript reference on the [Mozilla Developer Network][1], and I came across something called `&quot;strict mode&quot;`. I read it over and I&#39;m having trouble understanding what it does. Can someone briefly explain (in general) what its purpose is and how it is useful?

  [1]: https://en.wikipedia.org/wiki/MDN_Web_Docs


What is &quot;strict mode&quot; and how is it used?

I&#39;ve looked around the internet and haven&#39;t quite found what I&#39;m looking for. I have a flat array with each element containing an &#39;id&#39; and a &#39;parent_id&#39;. Each element will only have ONE parent, but may have multiple children. If the parent_id = 0, it is considered a root level item. I&#39;m trying to get my flat array into a tree. The other samples I have found only only copy the element to the parent, but the original still exists.

**EDIT**

Each element of the starting array is read from a separate XML file. The file itself will have &#39;0&#39; as the value for parent_id if it doesn&#39;t have a parent. The keys are actually strings.

I&#39;m sorry for the confusion earlier. Hopefully this is more clear:

**/EDIT**

My starting array:

&lt;pre&gt;
Array
(
    [_319_] =&gt; Array
        (
            [id] =&gt; 0
            [parent_id] =&gt; 0
        )

    [_320_] =&gt; Array
        (
            [id] =&gt; _320_
            [parent_id] =&gt; 0
        )

    [_321_] =&gt; Array
        (
            [id] =&gt; _321_
            [parent_id] =&gt; _320_
        )

    [_322_] =&gt; Array
        (
            [id] =&gt; _322_
            [parent_id] =&gt; _321_
        )

    [_323_] =&gt; Array
        (
            [id] =&gt; _323_
            [parent_id] =&gt; 0
        )

    [_324_] =&gt; Array
        (
            [id] =&gt; _324_
            [parent_id] =&gt; _323_
        )

    [_325_] =&gt; Array
        (
            [id] =&gt; _325_
            [parent_id] =&gt; _320_
        )
)&lt;/pre&gt;

The resulting array after the tree is made:

&lt;pre&gt;
Array
(
    [_319_] =&gt; Array
        (
            [id] =&gt; _319_
            [parent_id] =&gt; 0
        )

    [_320_] =&gt; Array
        (
            [id] =&gt; _320_
            [parent_id] =&gt; 0
            [children] =&gt; Array
                (
                    [_321_] =&gt; Array
                        (
                            [id] =&gt; _321_
                            [parent_id] =&gt; _320_
                            [children] =&gt; Array
                                (
                                    [_322_] =&gt; Array
                                        (
                                            [id] =&gt; _322_
                                            [parent_id] =&gt; _321_
                                        )
                                )
                        )
                    [_325_] =&gt; Array
                        (
                            [id] =&gt; _325_
                            [parent_id] =&gt; _320_
                        )
                )
    [_323_] =&gt; Array
        (
            [id] =&gt; _323_
            [parent_id] =&gt; 0
            [children] =&gt; Array
                (
                    [_324_] =&gt; Array
                        (
                            [id] =&gt; _324_
                            [parent_id] =&gt; _323_
                        )
                )
        )
&lt;/pre&gt;

Any help / guidance is greatly appreciated!

Some code I have so far:

&lt;pre&gt;

        function buildTree(array &amp;$elements, $parentId = 0) {
        $branch = array();
    
        foreach ($elements as $element) {
            if ($element[&#39;parent_id&#39;] == $parentId) {
                $children = $this-&gt;buildTree($elements, $element[&#39;id&#39;]);
                if ($children) {
                    $element[&#39;children&#39;] = $children;
                }
                $branch[] = $element;
            }
        }
    
        return $branch;
    }

&lt;/pre&gt;

Build a tree from a flat array in PHP

In CLRS, third Edition, on page 155, it is given that in MAX-HEAPIFY,

&gt; The children’s subtrees each have size at most **2n/3**—the worst case
&gt; occurs when the bottom level of the tree is exactly half full.

I understand why it is worst when the bottom level of the tree is exactly half full. And it is also answered in this question https://stackoverflow.com/questions/6859514/worst-case-in-max-heapify

My question is how to get 2n/3? 

Why if the bottom level is half full, then the size of the child tree is up to 2n/3?

How to calculate that?

Thanks


Worst case in Max-Heapify - How do you get 2n/3?

Consider there are some lists of integers as:

    #--------------------------------------
    0 [0,1,3]
    1 [1,0,3,4,5,10,...]
    2 [2,8]
    3 [3,1,0,...]
    ...
    n []
    #--------------------------------------

The question is to merge lists having at least one common element. So the results only for the given part will be as follows:

    #--------------------------------------
    0 [0,1,3,4,5,10,...]
    2 [2,8]
    #--------------------------------------

**What is the most efficient way to do this on large data (elements are just numbers)?**
Is `tree` structure something to think about?
I do the job now by converting lists to `sets` and iterating for intersections, but it is slow! Furthermore I have a feeling that is so-elementary! In addition, the implementation lacks something (unknown) because some lists remain unmerged sometime! Having said that, if you were proposing self-implementation please be generous and provide a simple sample code [apparently **Python** is my favoriate :)] or pesudo-code.  
**Update 1:**
Here is the code I was using:

    #--------------------------------------
    lsts = [[0,1,3],
            [1,0,3,4,5,10,11],
            [2,8],
            [3,1,0,16]];
    #--------------------------------------

The function is (**buggy!!**):

    #--------------------------------------
    def merge(lsts):
        sts = [set(l) for l in lsts]
        i = 0
        while i &lt; len(sts):
            j = i+1
            while j &lt; len(sts):
                if len(sts[i].intersection(sts[j])) &gt; 0:
                    sts[i] = sts[i].union(sts[j])
                    sts.pop(j)
                else: j += 1                        #---corrected
            i += 1
        lst = [list(s) for s in sts]
        return lst
    #--------------------------------------

The result is:

    #--------------------------------------
    &gt;&gt;&gt; merge(lsts)
    &gt;&gt;&gt; [0, 1, 3, 4, 5, 10, 11, 16], [8, 2]]
    #--------------------------------------

**Update 2:**
To my experience the code given by **Niklas Baumstark** below showed to be a bit faster for the simple cases. Not tested the method given by &quot;Hooked&quot; yet, since it is completely different approach (by the way it seems interesting).
The testing procedure for all of these could be really hard or impossible to be ensured of the results. The real data set I will use is so large and complex, so it is impossible to trace any error just by repeating. That is I need to be 100% satisfied of the reliability of the method before pushing it in its place within a large code as a module. Simply for now **Niklas**&#39;s method is faster and the answer for simple sets is correct of course.  
**However how can I be sure that it works well for real large data set?** Since I will not be able to trace the errors visually!

**Update 3:**
Note that reliability of the method is much more important than speed for this problem. I will be hopefully able to translate the Python code to Fortran for the maximum performance finally.

**Update 4:**  
There are many interesting points in this post and generously given answers, constructive comments. I would recommend reading all thoroughly. Please accept my appreciation for the development of the question, amazing answers and constructive comments and discussion.



Python: simple list merging based on intersections

In Linux/KDE, I can see a directory as a tree. How can I do it in Windows 7?

Consider I do NOT mean &quot;Windows Explorer&quot;. This just shows the directories, I also want the files.

Tree view of a directory/folder in Windows?

So I have simple tree:

    class MyNode
    {
     public MyNode Parent;
     public IEnumerable&lt;MyNode&gt; Elements;
     int group = 1;
    }

I have a `IEnumerable&lt;MyNode&gt;`. I want to get a list of all `MyNode` (including inner node objects (`Elements`)) as one flat list `Where` `group == 1`. How to do such thing via LINQ?

Content Type	Original Author	Original Content on Stackoverflow
Question	ocoutts	View Question on Stackoverflow
Solution 1 - Javascript	ty.	View Answer on Stackoverflow
Solution 2 - Javascript	jnuno	View Answer on Stackoverflow
Solution 3 - Javascript	Raphaël Pellicier	View Answer on Stackoverflow
Solution 4 - Javascript	Stephen James	View Answer on Stackoverflow
Solution 5 - Javascript	AturSams	View Answer on Stackoverflow
Solution 6 - Javascript	Chaitanya Chandurkar	View Answer on Stackoverflow

What javascript tree data structures are available?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Solution 3 - Javascript

Solution 4 - Javascript

Solution 5 - Javascript

Solution 6 - Javascript

call to pure virtual function from base class constructor

What is Eclipse doing when it says that it's updating indexes?

Attributions