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• What is the usage of Splay Trees in the real world?

  - by Meena

  I decided to learn about balanced search trees, so I picked 2-3-4 and splay trees. What are the examples of splay trees usage in the real world? In this Cornell: http://www.cs.cornell.edu/courses/cs3110/2009fa/recitations/rec-splay.html I read that splay trees are 'A good example is a network router'. But from rest of the explanation seams like network routers use hash tables and not splay trees since the lookup time is constant instead of O(log n).

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• What is the usage of Spaly Trees in the real world?

  - by Meena

  I decided to learn about Balance search trees, so I picked 2-3-4 and splay trees. I'm wondering what are the examples of splay trees usage in the real world? In this Cornell: http://www.cs.cornell.edu/courses/cs3110/2009fa/recitations/rec-splay.html I read that splay trees are 'A good example is a network router'. But from rest of the explanation seams like network routers use hash tables and not splay trees since the lookup time is constant instead of O(log n). thanks!

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• Dynamic quadrees

  - by paul424

  recently I come out writing Quadtree for creatures culling in Opendungeons game. Thing is those are moving points and bounding hierarchy will quickly get lost if the quadtree is not rebuild very often. I have several variants, first is to upgrade the leaf position , every time creature move is requested. ( note if I would need collision detection anyway, so this might be necessery anyway). Second would be making leafs enough large , that the creature would sure stay inside it's bounding box ( due to its speed limit). The partition of a plane in quadtree is always fixed ( modulo the hierarchical unions of some parts) . For creatures close to the center of the plane , there would be no way of keeping it but inside one big leaf, besides this brokes the invariant that each point can be put into any small area as desired. So on the second thought could I use several quadrees ? Each would have its "coordinate axis XY" somwhere shifted ? Before I start playing with this maybe some other space diving structure would suit me better, unfortunetly wiki does not compare it's execution time : http://en.wikipedia.org/wiki/Grid_%28spatial_index%29#See_also

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• Fast language for problem solving? [closed]

  - by Friend of Kim

  I learned PHP to make websites. After some years I've started using programming for solving what is difficult tasks for my level. Now I want to make a program that solves equations. (I want to write it myself, not use an API. Because I'm doing this for the sake of the challenge, not for the result..) Because of this, I'm going to learn a new and faster/better language. It's going to be C++, Java, Python or C#. What are the benefits of each language, and which language is best for speed compared to speed of writing and readability? Using C would be lightning fast, but the lack of OO is making for more complex code and reduces the readability, for example..

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• async tree jquery easy ui

  - by user765368

  I'm trying to create an Async Tree in jQuery Easy Ui. I understand the idea behind it, but will this work if my root node is not a node that is coming from the database or something (therefore, it does not have any id). My root node is some node that I define myself. How would I make an async tree in jquery easy ui to load a bunch of nodes as children of my root node (which, again has no id because it's not coming from the database. My children nodes are coming from the database though). I hope y'all understand what I'm trying to do here. Any help please

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• How to add add node in binary tree

  - by m.qayyum

  (5)Root (3)-------^--------(7) (2)---^----(5) ^-----(8) i want to add node with data 5 in this binray tree....Please help.....i really stuck in it

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• Tree View / File View Control for C#

  - by Jason

  I have been looking for a C# tree control for displaying a file system that has the following capabilities: Select a starting directory. I don't always want to start at a "default" top directory level. The ability to grab an event when the user double clicks on a file in the tree. I want to handle opening the file within my application. I have been looking at this C# File Browser. Unfortunately, I have not been able to figure out how to do meet my second need. (If anybody can clear that up for me, I would like that even better.) Thanks for any help.

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• complicated graphviz tree structure

  - by thomas

  Hello. I am trying to create a tree structure with graphviz. I am open to either writing the graphviz code by hand or using the ruby-graphviz gem for ruby. Given the below picture can anyone provide any insight on the necessary code? Ignore that the lines are not straight...they should be when graphviz builds the graph. I am open to having dots/points when lines intersect as well. I have played with ruby-graphviz and the family tree class...this is getting me part of the way there but I really need all lines to be straight and intersect at right angles and the out-of-the-box code doesn't seem to do that.

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• JavaScript tree / treegrid libraries

  - by desau

  I'm looking for a good JavaScript tree / treegrid package. Now -- before you answer: It needs to be able to perform well with lots of nodes. Perhaps 1,000 sibling nodes. It needs to be able to draw to a usable state within 2 or 3 seconds with 1,000 nodes. It doesn't necessarily need to draw all 1,000 nodes at once -- if it supports some sort of "smart rendering" or fake scrolling. Beyond that, column resizing, drag and drop, inline editing would all be nice, although I could probably add that functionality myself. I've already tried dojo's tree and yahoo's YUI treeview. Both are too slow.

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• Build and render infinite hierarchical category tree from self-referential category table

  - by FreshCode

  I have a Categories table in which each category has a ParentId that can refer to any other category's CategoryId that I want to display as multi-level HTML list, like so: <ul class="tree"> <li>Parent Category <ul> <li>1st Child Category <!-- more sub-categories --> </li> <li>2nd Child Category <!-- more sub-categories --> </li> </ul> </li> </ul> Presently I am recursively rendering a partial view and passing down the next category. It works great, but it's wrong because I'm executing queries in a view. How can I render the list into a tree object and cache it for quick display every time I need a list of all hierarchical categories?

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• MS SQL server and Trees

  - by Julian

  Im looking for some way of extrating data form a tree table as defined below. Table Tree Defined as :- TreeID uniqueidentifier TreeParent uniqueidentifier TreeCode varchar(50) TreeDesc varchar(100) Data some (23k rows), Parent Refs back into ID in table The following SQL renders the whole tree (takes arround 2 mins 30) I need to do the following. 1) Render each Tree Node with its LVL 1 parent 2) Render all nodes that have a Description that matches a TreeDesc like 'SomeText%' 3) Render all parent nodes that are for a single tree id. Items 2 and 3 take 2mins30 so this needs to be a lot faster! Item 1, just cant work out how to do it with out killing SQL or taking forever any sugestions would be helpfull Thanks Julian WITH TreeCTE(TreeCode, TreeDesc, depth, TreeParent, TreeID) AS ( -- anchor member SELECT cast('' as varchar(50)) as TreeCode , cast('Trees' as varchar(100)) as TreeDesc, cast('0' as Integer) as depth, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier) as TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier) as TreeID UNION ALL -- recursive member SELECT s.TreeCode, s.TreeDesc, cte.depth+1, isnull(s.TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)), isnull(s.TreeID, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) FROM pdTrees AS S JOIN TreeCTE AS cte ON isnull(s.TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) = isnull( cte.TreeID , cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) ) -- outer query SELECT s.TreeID, s.TreeCode, s.TreeDesc, s.depth, s.TreeParent FROM TreeCTE s

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• a general tree implementation in python

  - by vishnu

  i want to build a general tree in which a root node contains 'n' childrens and those childrens may contain other childrens.....

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• Code to apply expression tree directly to List

  - by Gamma Vega

  Is there a method call in Linq that will apply a expression tree directly on a List<V>? For instance, if I have a expression tree that is built on Order type, and i have a collection of List<Order> items on which i need to apply this expression. I am looking something similar to: class OrderListStore : IQueryable<V>, <other interfaces required to implement custom linq provider> { List<Order> orders; public Expression Expression { get { return Expression.Constant(this); } } IEnumerator<V> IEnumerable<V>.GetEnumerator() { //Here I need to have a method that will take the existing expression //and directly apply on list something like this .. Expression.Translate(orders); } } Any help in this regard is highly appreciated.

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• Code Golf Christmas Edition: How to print out a Christmas tree of height N

  - by TheSoftwareJedi

  Given a number N, how can I print out a Christmas tree of height N using the least number of code characters? N is assumed constrained to a min val of 3, and a max val of 30 (bounds and error checking are not necessary). N is given as the one and only command line argument to your program or script. All languages appreciated, if you see a language already implemented and you can make it shorter, edit if possible - comment otherwise and hope someone cleans up the mess. Include newlines and whitespace for clarity, but don't include them in the character count. A Christmas tree is generated as such, with its "trunk" consisting of only a centered "*" N = 3: * *** ***** * N = 4: * *** ***** ******* * N = 5: * *** ***** ******* ********* * N defines the height of the branches not including the one line trunk. Merry Christmas SO!

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• DevExpress>TcxDBTreeList Drag-Drop Tree Nodes (records)

  - by adnan

  I want to move tree nodes (db records) in TcxDBTreeList by dragging, is there a property on this component for this option ?

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• UVa #112 Tree Summing

  - by unclerojelio

  I'm working on UVa #112 Tree Summing. I have what I think should be a working solution but it is not accepted by the online judge due to a basic misunderstanding of the problem on my part. Consider the following inputs: -1 (-1()()) 77 (77(1()())()) or diagrammatically, the trees look like: -1 77 / \ / \ () () 1 () / \ () () According to at least two working solutions, the correct output for the above inputs is: yes no However, I don't understand why the second one should be 'no'. It looks to me like the rightmost path of the tree should give the proper sum. What am I missing?

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• Java or php tree structure problem

  - by agazerboy

  Hi All, I have all my data in my database. It has following 4 columns id source_clust target_clust result_clust 1 7 72 649 2 9 572 650 3 649 454 651 4 32 650 435 This data is like tree structure. source_clust and target_clust generate target_clust. target_clust can be source_clust or target_clust to make a new target_clust. Is there any php function or class that I can use to generate tree structure for my data???? I see this MySql site they are doing exactly what I need but I couldn't find how to implement that query in my data. Thanks ! Edited Is there any way in java to do it? if we have same data in array ??

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• Guidelines to an Iterator Class

  - by isurulucky

  Hi, I have a Red Black tree implemented in c++. It supports the functionality of a STL map. Tree nodes contain keys and the values mapped. I want to write an iterator class for this, but I'm stuck with how to do it. Should I make it an inner class of the Tree class? Can anyone give me some guidelines on how to write it + some resources?? Thank You!!

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• Looking for a better design: A readonly in-memory cache mechanism

  - by Dylan Lin

  Hi all, I have a Category entity (class), which has zero or one parent Category and many child Categories -- it's a tree structure. The Category data is stored in a RDBMS, so for better performance, I want to load all categories and cache them in memory while launching the applicaiton. Our system can have plugins, and we allow the plugin authors to access the Category Tree, but they should not modify the cached items and the tree(I think a non-readonly design might cause some subtle bugs in this senario), only the system knows when and how to refresh the tree. Here are some demo codes: public interface ITreeNode<T> where T : ITreeNode<T> { // No setter T Parent { get; } IEnumerable<T> ChildNodes { get; } } // This class is generated by O/R Mapping tool (e.g. Entity Framework) public class Category : EntityObject { public string Name { get; set; } } // Because Category is not stateless, so I create a cleaner view class for Category. // And this class is the Node Type of the Category Tree public class CategoryView : ITreeNode<CategoryView> { public string Name { get; private set; } #region ITreeNode Memebers public CategoryView Parent { get; private set; } private List<CategoryView> _childNodes; public IEnumerable<CategoryView> ChildNodes { return _childNodes; } #endregion public static CategoryView CreateFrom(Category category) { // here I can set the CategoryView.Name property } } So far so good. However, I want to make ITreeNode interface reuseable, and for some other types, the tree should not be readonly. We are not able to do this with the above readonly ITreeNode, so I want the ITreeNode to be like this: public interface ITreeNode<T> { // has setter T Parent { get; set; } // use ICollection<T> instead of IEnumerable<T> ICollection<T> ChildNodes { get; } } But if we make the ITreeNode writable, then we cannot make the Category Tree readonly, it's not good. So I think if we can do like this: public interface ITreeNode<T> { T Parent { get; } IEnumerable<T> ChildNodes { get; } } public interface IWritableTreeNode<T> : ITreeNode<T> { new T Parent { get; set; } new ICollection<T> ChildNodes { get; } } Is this good or bad? Are there some better designs? Thanks a lot! :)

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• Modifying JSF Component Tree in PhaseListener

  - by jamiebarrow

  Hi all, I'm having an issue. I've implemented a PhaseListener, which is meant to add a style class to any UIInput components in the tree that have messages attached to them, and removes the style class if it doesn't have any messages attached to them. The PhaseListener runs in the RENDER_RESPONSE phase, and does it's work in both the beforePhase and afterPhase methods while debugging. While debugging, I found that beforePhase doesn't have access to the full component tree, but afterPhase does. Any changes done in afterPhase aren't rendered though. How do I go about this? I want this to be completely server side. Thanks, James

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• Entropy using Decision Tree's

  - by Matt Clements

  Train a decision tree on the data represented by attributes A1, A2, A3 and outcome C described below: A1 A2 A3 C 1 0 1 0 0 1 1 1 0 0 1 0 For log2(1/3) = 1.6 and log2(2/3) = 0.6, answer the following questions: a) What is the value of entropy H for the given set of training example? b) What is the portion of the positive samples split by attribute A2? c) What is the value of information gain, G(A2), of attribute A2? d) What is IFTHEN rule(s) for the decision tree?

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• Problem building a complete binary tree of height 'h' in Python

  - by Jack

  Here is my code. The complete binary tree has 2^k nodes at depth k. class Node: def __init__(self, data): # initializes the data members self.left = None self.right = None self.data = data root = Node(data_root) def create_complete_tree(): row = [root] for i in range(h): newrow = [] for node in row: left = Node(data1) right = Node(data2) node.left = left node.right = right newrow.append(left) newrow.append(right) row = copy.deepcopy(newrow) def traverse_tree(node): if node == None: return else: traverse_tree(node.left) print node.data traverse_tree(node.right) create_complete_tree() print 'Node traversal' traverse_tree(root) The tree traversal only gives the data of root and its children. What am I doing wrong?

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• Precompile Lambda Expression Tree conversions as constants?

  - by Nathan

  It is fairly common to take an Expression tree, and convert it to some other form, such as a string representation (for example this question and this question, and I suspect Linq2Sql does something similar). In many cases, perhaps even most cases, the Expression tree conversion will always be the same, i.e. if I have a function public string GenerateSomeSql(Expression<Func<TResult, TProperty>> expression) then any call with the same argument will always return the same result for example: GenerateSomeSql(x => x.Age) //suppose this will always return "select Age from Person" GenerateSomeSql(x => x.Ssn) //suppose this will always return "select Ssn from Person" So, in essence, the function call with a particular argument is really just a constant, except time is wasted at runtime re-computing it continuously. Assuming, for the sake of argument, that the conversion was sufficiently complex to cause a noticeable performance hit, is there any way to pre-compile the function call into an actual constant?

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• View a git diff-tree in a reasonable format

  - by Josh

  Howdy, I'm about to do a git svn dcommit to our svn repo -- and as is recommended in a number of places, I wanted to figure out exactly what I was going to be committing with a dry run. As such I ran: git svn dcommit -n This produced output: Committing to http://somerepo/svn/branches/somebranch diff-tree 1b937dacb302908602caedf1798171fb1b7afc81~1 1b937dacb302908602caedf1798171fb1b7afc81 How do I view this in a format that I can consume as a human? A list of modified files comes to mind. This is probably easy, but running git diff-tree on those hashes gives me a reference to a directory and a some other hashes, as well as some numbers. Not quite sure what to make of it. Thanks very much, Josh

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• php tree structure problem

  - by agazerboy

  Hi All, I have all my data in my database. It has following 4 columns id source_clust target_clust result_clust 1 7 72 649 2 9 572 650 3 649 454 651 4 32 650 435 This data is like tree structure. source_clust and target_clust generate target_clust. target_clust can be source_clust or target_clust to make a new target_clust. Is there any php function or class that I can use to generate tree structure for my data???? I see this MySql site they are doing exactly what I need but I couldn't find how to implement that query in my data. Thanks !

  Read the article

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