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• Any tips of how to handle hierarchial trees in relational model?

  - by George

  Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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• Binary tree to BST

  - by dsiap

  How wil you convert Binary Tree to Binary Search Tree with O(n) extra space ?

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• [Ext.tree.TreePanel] getNodeById does not work

  - by Moon

  Hi, I have a ext treepanel with json. var tree = new Ext.tree.TreePanel({ renderTo:'tree-container', title: 'Category', height: 300, width: 400, useArrows:true, autoScroll:true, animate:true, enableDD:true, containerScroll: true, rootVisible: false, frame: true, root: { text: 'Category', draggable: false, id: '0' }, // auto create TreeLoader dataUrl: $("#web").val() + "/category/index/get-nodes", listeners: { 'checkchange': function(node, checked){ if(checked){ categoryManager.add(node.id); //node.getUI().addClass('complete'); }else{ categoryManager.remove(node.id); // node.getUI().removeClass('complete'); } } } }); dataUrl loads the following json code [{"text":"Code Snippet","id":"1","cls":"folder","checked":false,"children":[{"text":"PHP","id":"3","cls":"file","checked":false,"children":[]},{"text":"Javascript","id":"4","cls":"file","checked":false,"children":[]}]}] when I try to find a node by console.log( tree.getNodeByid(3) ), it shows that it is undefined. Do I have a problem with my code?

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• Git: Find duplicate blobs (files) in this tree

  - by Readonly

  This is sort of a follow-up to this question. If there are multiple blobs with the same contents, they are only stored once in the git repository because their SHA-1's will be identical. How would one go about finding all duplicate files for a given tree? Would you have to walk the tree and look for duplicate hashes, or does git provide backlinks from each blob to all files in a tree that reference it?

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• A question on getting number of nodes in a Binary Tree

  - by Robert

  Dear all, I have written up two functions (pseudo code) for calculation the number of nodes and the tree height of a Binary Tree,given the root of the tree. Most importantly,the Binary Tree is represented as the First chiled/next sibling format. so struct TreeNode { Object element; TreeNode *firstChild; TreeNode *nextSibling; } Calculate the # of nodes: public int countNode(TreeNode root) { int count=0; while(root!=null) { root= root.firstChild; count++; } return count; } public int countHeight(TreeNode root) { int height=0; while(root!=null) { root= root.nextSibling; height++; } return height; } This is one of the problem I saw on an algorithm book,and my solution above seems to have some problems,also I didn't quite get the points of using this First Child/right sibling representation of Binary Tree,could you guys give me some idea and feedback,please? Cheers!

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• Haskell Binary Tree Function (map)

  - by Bizarro

  How can i define a Haskell function which will apply a function to every value in a binary tree? So i know that it is similar to the map function - and that its type would be: mapT :: (a - b) - Tree a - Tree b but thats about it...

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• tree implementatoin in python

  - by JAY G

  how to implement tree in python???i am python beginner..plz help!!give me general idea

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• Rails - how to serialize a tree not in a form

  - by tiny_clanger

  I started with the standard scriptaculous drag and drop tree, and that all works fine. Then started implementing this: http://www.artweb-design.de/2008/5/30/scriptaculous-sortabletree which gives a good drag and drop tree Where I am stuck is how to get serialize the tree (unordered list)? It's not in a form, and I can't find a way to serialize it to move onto setting up the AJAX update.

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• jquery ajaxSubmit jquery file tree

  Hi, I'm using a jquery file tree and I'd like to allow users to upload files to whatever directory they're currently in. I am having an issue binding the form within the tree, though, since the tree is loading dynamically and obviously can't bind a form that doesn't exist. Any ideas would be greatly appreciated!

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• GWT: Editing Text Of Tree Item

  - by kirtcathey

  Hi All. When a user clicks a 'Add Node' button above a tree and the program adds a tree item below the selected node, I would like to insert the new tree item with the text highlight and ready for editing by the user... like labels in GMail. Any ideas? --Kirt

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• Why are trees shining in background?

  - by Kinected

  Currently I am creating a forest scene in the dark, and the trees are shining far away, but when I get close they are fine. I have the shaders set to "Nature/Tree Soft Occlusion [bark/leaves]", but they are still rendering strange far away, but close they are fine. I tried placing the trees in a folder named "Ambient-Occlusion" like said here, but no luck. Also fog is turned off. Thanks in advance.

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• Is there a minimum spanning tree that does not contain the min/max weighted edge?

  - by Martin

  If we have an (arbitrary) connected undirected graph G, whose edges have distinct weights, does every MST of G contains the minimum weighted edge? is there an MST of G that does not contain the maximum weighted edge? Also, I'm more thankful if someone can give a hint of the key things one must keep in mind when dealing with such MST questions. Thanks

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• Using C# and gppg, how would I construct an abstract syntax tree?

  - by Rupert

  Is there a way to do this almost out-of-the-box? I could go and write a big method that would use the collected tokens to figure out which leaves should be put in which branches and in the end populate a TreeNode object, but since gppg already handled everything by using supplied regular expressions, I was wondering if there's an easier way? Even if not, any pointers as to how best to approach the problem of creating an AST would be appreciated. Apologies if I said anything silly, I'm only just beginning to play the compiler game. :)

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• How to set initial checked values of rich tree leaf node.

  - by Ajay99

  Hi, How to set the initial the leaf node values. -----------------------Stations.xml AAAAAAAAAAAA BBBBBBBBBBBB CCCCCCCCCC DDDDDDDDDDDD EEEEEEEEEEEEEE Hall Oates - Kiss On My List David Bowie - Let's Dance Lyn Collins - Think (About It) Kim Carnes - Bette Davis Eyes KC the Sunshine Band - Give It Up //inital check values --------------------Libray.java---------------- public class Library { private TreeNode treeData; private List menus=null; public Library()throws Exception { menus=new ArrayList(); //it's initial selection of the check box vardata.attributes.selection("---key1---); vardata.attributes.selection("---key2---); vardata.attributes.selection("---keyn---); yoursuggestedcode.attribute.selection("key"); //I need your suggestion code. FacesContext context = FacesContext.getCurrentInstance(); treeData = XmlTreeDataBuilder.build(new InputSource(getClass().getResourceAsStream("/Stations.xml"))); } public TreeNode getTreeData() { return treeData; } public void setTreeData(TreeNode treeData) { this.treeData = treeData; } public List getMenus() { return menus; } public void setMenus(List menus) { this.menus = menus; }

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• In GWT-EXT checkboxtree how to handle single selection of tree nodes?

  - by RAS

  hi, I'm working on checkBoxTree in GWT-EXT 2.0.3 with Java. My aim is to get a selectionModel which allows me to select(check) only one TreeNode at a time. If I select another TreeNode after selecting one then, the previous one should be unchecked. I've tried using DefaultSelectionModel with TreePanel, but either I've not used it properly or it's working only for selection of TreeNode not for checking a TreeNode. Can anyone help me in this? Thanks in advance.

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• What is the difference between tree depth and height?

  - by Gabriel Šcerbák

  This is a simple question from algorithms theory. The difference between them is that in one case you count number of nodes and in other number of edges on the shortest path between root and concrete node. Which is which?

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• Python - Is there a better/efficient way to find a node in tree?

  - by Sej P

  I have a node data structure defined as below and was not sure the find_matching_node method is pythonic or efficient. I am not well versed with generators but think there might be better solution using them. Any ideas? class HierarchyNode(): def __init__(self, nodeId): self.nodeId = nodeId self.children = {} # opted for dictionary to help reduce lookup time def addOrGetChild(self, childNode): return self.children.setdefault(childNode.nodeId,childNode) def find_matching_node(self, node): ''' look for the node in the immediate children of the current node. if not found recursively look for it in the children nodes until gone through all nodes ''' matching_node = self.children.get(node.nodeId) if matching_node: return matching_node else: for child in self.children.itervalues(): matching_node = child.find_matching_node(node) if matching_node: return matching_node return None

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• In Python ElementTree how can I get list of all ancestors of an element in tree ?

  - by Rohit

  I need "get_ancestors_recursively" function. A sample run can be >>> dump(tr) <anc1> <anc2> <element> </element> </anc2> </anc1> >>> input_element = tr.getiterator("element")[0] >>> get_ancestors_recursively(input_element) ['anc1', 'anc2'] Can somebody help me with this ?

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• How many elements can be held in a B-tree of order n?

  - by Phenom

  Is it 2n? Just checking.

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• tic tac toe game ai as3

  - by David Jones

  I'm looking into creating a simple tic tac toe/noughts and crosses game in actionscript3 and am trying to understand the ideas behind the ai used in a game like this. I've seen some simplistic examples online but from what I've read a game tree or something like minimax is the best way to go about this. Can anyone help explain or reference any good examples of this? I've seen that there is a library called as3ds - data structures for game developers which has a number of classes that might help tie this together? Any info/examples or help is much appreciated

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• Tic-Tac-Toe game AI

  - by David Jones

  I'm looking into creating a simple tic tac toe/noughts and crosses game in Actionscript3 and am trying to understand the ideas behind the AI used in a game like this. I've seen some simplistic examples online but from what I've read a game tree or something like minimax is the best way to go about this. Can anyone help explain or reference any good examples of this? I've seen that there is a library called as3ds - data structures for game developers which has a number of classes that might help tie this together? Any info/examples or help is much appreciated.

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• Are there any good Java/JVM libraries for my Expression Tree architecture?

  - by Snuggy

  My team and I are developing an enterprise-level application and I have devised an architecture for it that's best described as an "Expression Tree". The basic idea is that the leaf nodes of the tree are very simple expressions (perhaps simple values or strings). Nodes closer to the trunk will get more and more complex, taking the simpler nodes as their inputs and returning more complex results for their parents. Looking at it the other way, the application performs some task, and for this it creates a root expression. The root expression divides its input into smaller units and creates child expressions, which when evaluated it can use to build it's own result. The subdividing process continues until the simplest leaf nodes. There are two very important aspects of this architecture: It must be possible to manipulate nodes of the tree after it is built. The nodes may be given new input values to work with and any change in result for that node needs to be propagated back up the tree to the root node. The application must make best use of available processors and ultimately be scalable to other computers in a grid or in the cloud. Nodes in the tree will often be updating concurrently and notifying other interested nodes in the tree when they get a new value. Unfortunately, I'm not at liberty to discuss my actual application, but to aid understanding a little bit, you might imagine a kind of spreadsheet application being implemented with a similar architecture, where changes to cells in the table are propagated all over the place to other cells that need the result. The spreadsheet could get so massive that applying multi-core multi-computer distributed system to solve it would be of benefit. I've got my prototype "Expression Engine" working nicely on a single multi-core PC but I've started to run into a few concurrency issues (as expected because I haven't been taking too much care so far) so it's now time to start thinking about migrating the Engine to a more robust library, and that leads to a number of related questions: Is there any precedent for my "Expression Tree" architecture that I could research? What programming concepts should I consider. I realise this approach has many similarities to a functional programming style, and I'm already aware of the concepts of using futures and actors. Are there any others? Are there any languages or libraries that I should study? This question is inspired by my accidental discovery of Scala and the Akka library (which has good support for Actors, Futures, Distributed workloads etc.) and I'm wondering if there is anything else I should be looking at as well?

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• WPF tree data binding

  - by Am

  Hi, I have a well defined tree repository. Where I can rename items, move them up, down, etc. Add new and delete. The data is stored in a table as follows: Index Parent Label Left Right 1 0 root 1 14 2 1 food 2 7 3 2 cake 3 4 4 2 pie 5 6 5 1 flowers 8 13 6 5 roses 9 10 7 5 violets 11 12 Representing the following tree: (1) root (14) (2) food (7) (8) flowers (13) (3) cake (4) (5) pie (6) (9) roeses (10) (11) violets (12) or root food cake pie flowers roses violets Now, my problem is how to represent this in a bindable way, so that a TreeView can handle all the possible data changes? Renaming is easy, all I need is to make the label an updatble field. But what if a user moves flowers above food? I can make the relevant data changes, but they cause a complete data change to all other items in the tree. And all the examples I found of bindable hierarchies are good for non static trees.. So my current (and bad) solution is to reload the displayed tree after relocation change. Any direction will be good. Thanks

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• Binary Search Tree for specific intent

  - by Luís Guilherme

  We all know there are plenty of self-balancing binary search trees (BST), being the most famous the Red-Black and the AVL. It might be useful to take a look at AA-trees and scapegoat trees too. I want to do deletions insertions and searches, like any other BST. However, it will be common to delete all values in a given range, or deleting whole subtrees. So: I want to insert, search, remove values in O(log n) (balanced tree). I would like to delete a subtree, keeping the whole tree balanced, in O(log n) (worst-case or amortized) It might be useful to delete several values in a row, before balancing the tree I will most often insert 2 values at once, however this is not a rule (just a tip in case there is a tree data structure that takes this into account) Is there a variant of AVL or RB that helps me on this? Scapegoat-trees look more like this, but would also need some changes, anyone who has got experience on them can share some thougts? More precisely, which balancing procedure and/or removal procedure would help me keep this actions time-efficient?

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• "Subforms" associated with tree view in VB

  - by knomdeguerre

  I am using VB Express 2008 to demonstrate my ideas for an improved UI for an existing product for my colleagues at work. The current UI has a certain page with ten tabs, allowing the user to define up to ten "things". The available choices for each of the ten "things" are all the same. On each of the ten tabs, there is a checkbox to enable that definition. Generally, a user will never use more than 5 or 6 unique definitions, the rest will remain disabled. So far, my prototype has a tree view control with one branch to contain this list of definitions, Add and Delete buttons. My idea is: there is one sub-branch to start with (corresponding to the first tab in the current UI); if the user wants addtional definitions, they click Add and other branches are added to the tree view, up to maximum of ten. I think I should be able to create a "class" that has a sub-UI (like a sub-form in Access) along with behavior code, that can be instantiated with each press of the Add button; each instantiation's settings can be set independently and is displayed in the main UI form )in a panel or frame) when selected in the tree view. For example, suppose the user Adds to make a total of three definitions: the tree view now has three sub-branches, each of which presents the same sub-UI with settings that can be set specific to the selected sub-branch. I'm sure it's possible but not sure how to do it. I know a comprehensive "answer" might be complicated and long, but I may just need some quick hints to get underway - don't be shy! Thanks in advance!

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