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  • Spatial Index for Rectangles With Fast Insert

    - by TheCloudlessSky
    Hello, I'm looking for a data structure that provides indexing for Rectangles. I need the insert algorithm to be as fast as possible since the rectangles will be moving around the screen (think of dragging a rectangle with your mouse to a new position). I've looked into R-Trees, R+Trees, kD-Trees, Quad-Trees and B-Trees but from my understanding insert's are usually slow. I'd prefer to have inserts at sub-linear time complexity so maybe someone can prove me wrong about either of the listed data structures. I should be able to query the data structure for what rectangles are at point(x, y) or what rectangles intersect rectangle(x, y, width, height). EDIT: The reason I want insert so fast is because if you think of a rectangle being moved around the screen, they're going to have to be removed and then re-inserted. Thanks!

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  • Parse Directory Structure (Strings) to JSON using PHP

    - by Ecropolis
    I have an array of file-path strings like this videos/funny/jelloman.wmv videos/funny/bellydance.flv videos/abc.mp4 videos/june.mp4 videos/cleaver.mp4 fun.wmv jimmy.wmv herman.wmv Is there a library or easy way I can get to a data structure json or xml? Something like this: (I see there are a lot of snippets available for traversing actual folders, but again, I just have strings.) { files:{ file:[ { filename:'fun.wmv' }, { filename:'jimmy.wmv' }, { filename:'herman.wmv' } ], folder:{ foldername:'videos', file:[ { filename:'abc.mp4' }, { filename:'june.mp4' }, { filename:'cleaver.mp4' } ], folder:{ foldername:'funny', file:[ { filename:'jelloman.wmv' }, { filename:'bellydance.flv' } ] } } } }

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  • How to find nth element from the end of a singly linked list?

    - by Codenotguru
    The following function is trying to find the nth to last element of a singly linked list. For example: If the elements are 8->10->5->7->2->1->5->4->10->10 then the result is 7th to last node is 7. Can anybody help me on how this code is working or is there a better and simpler approach? LinkedListNode nthToLast(LinkedListNode head, int n) { if (head == null || n < 1) { return null; } LinkedListNode p1 = head; LinkedListNode p2 = head; for (int j = 0; j < n - 1; ++j) { // skip n-1 steps ahead if (p2 == null) { return null; // not found since list size < n } p2 = p2.next; } while (p2.next != null) { p1 = p1.next; p2 = p2.next; } return p1; }

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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 !

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  • Are there any implementations of multiset for .Net?

    - by dangph
    I'm looking for a .Net implementation of a multiset. Can anyone recommend a good one? (A multiset, or bag, is a set that can have duplicate values, and on which you can do set operations: intersection, difference, etc. A shopping cart for instance could be thought of as a multiset because you can have multiple occurrences of the same product.)

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  • Does std::multiset guarntee insertion order?

    - by Naveen
    I have a std::multiset which stores elements of class A. I have provided my own implementation of operator< for this class. My question is if I insert two equivalent objects into this multiset is their order guaranteed? For example, first I insert a object a1 into the set and then I insert an equivalent object a2 into this set. Can I expect the a1 to come before a2 when I iterate through the set? If no, is there any way to achieve this using multiset?

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  • Thread-safe data structure design

    - by Inso Reiges
    Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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  • how can we make class with Linked list recursion ...

    - by epsilon_G
    Hi , I'm newbee in The C++ heaven and the OOP, ... I'd like to make some stuffs with the Data structures ... However,I'd like to merge two linked listes ... I made a class before "List" wich contain all what I need to programme something with List ... Add , Display .. The probleme is that I programmed the function "Merge2lists" which give us the third list .. How can I display the third list in the main program after using "Merge2lists" Plz , my prob with the Class and the OOP syntaxe ... try to give me the implementation in the main program ??? Otherwise,How can I apply function given pointer in main program wich declared in class .. Thankx class Liste { private: struct node { int elem ; node *next; }*p; public: LLC(); void Merge2lists (node* a, node * b,node *&result); ~LLC(); }; void List::Merge2lists (node* a, node * b,node *&result) { result = NULL; if (a==NULL) { result=b; return;} else if (b==NULL) { result=a; return;} if (a->elem <= b->elem) { result = a; Merge2lists(a->next, b,result->next); } else { result = b; Merge2lists(a, b->next,result->next); } return; } int main() { liste a ; a.Aff_Val(46); a.Aff_Val(54); a.add_as_first(2); a.add_as_first(1); a.Display(); /*This to displat the elemnts ... Don't care about it it's easy to make*/ list liste2; b.Add(2); b.Add(14); b.Add(16); list result; Merge2lists (a,b,result); /*The probleme is here , how can I use this in my program */

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  • Display `pretty output` of directory content from array

    - by user275074
    Hi, I'm using the following code to get an array of directories and their sub-directories where each contain file type extension: png. It works great but I need to be able to output the results of the array in a list style format e.g. Test - test2.png - test1.png subfolder - test3.png sub sub folder - test4.png etc Code: $filter=".png"; $directory='../test'; $it=new RecursiveDirectoryIterator("$directory"); foreach(new RecursiveIteratorIterator($it) as $file){ if(!((strpos(strtolower($file),$filter))===false)||empty($filter)){ $items[]=preg_replace("#\\\#", "/", $file); } } Example array of results: array ( 0 => '../test/test2.png', 1 => '../test/subfolder/subsubfolder/test3.png', 2 => '../test/subfolder/test3.png', 3 => '../test/test1.png', ) What would be the best way of achieving the desired result?

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  • Does std::multiset guarantee insertion order?

    - by Naveen
    I have a std::multiset which stores elements of class A. I have provided my own implementation of operator< for this class. My question is if I insert two equivalent objects into this multiset is their order guaranteed? For example, first I insert a object a1 into the set and then I insert an equivalent object a2 into this set. Can I expect the a1 to come before a2 when I iterate through the set? If no, is there any way to achieve this using multiset?

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  • Tree data structure in php

    - by Piyush
    in my application user starts a new tree or get added under a child-user and keep on adding users in branches in such a way- >there are 10 level of tree type structure. >root node contain 1 user and each node(user) can have max 5 child-user in this way tree will be like level 0 = 1 user , level 1 = 5 user, level 2 = 25 user , level 3 = 125 user and so on. I created one MySQL table having columns like- User_id , level, super_id, child1_id, child2_id, child3_id, child4_id, child5_id my question is How can I get all child-user(child to child also) of a particular user at any level do I need to add some more columns in my table??

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  • Javascript : where are high level data structures?

    - by user355056
    Hi! I'm writing a client program for a game in Javascript but I'm new in Javascript world. Core Javascript lack of high level data structures. I've found code snippets on internet but I'm looking for a reference library (like commons-collection or google-collection in java world). I found this post: http://stackoverflow.com/questions/2523436/javascript-implementation-of-a-set-data-structure which refers to jshashtable and closure. Are they reference implementations? Do you know something else? Thanks

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  • C# recursive programming with lists

    - by David Torrey
    I am working on a program where each item can hold an array of items (i'm making a menu, which has a tree-like structure) currently i have the items as a list, instead of an array, but I don't feel like I'm using it to its full potential to simplify code. I chose a list over a standard array because the interface (.add, .remove, etc...) makes a lot of sense. I have code to search through the structure and return the path of the name (i.e. Item.subitem.subsubitem.subsubsubitem). Below is my code: public class Item { //public Item[] subitem; <-- Array of Items public List<Item> subitem; // <-- List of Items public Color itemColor = Color.FromArgb(50,50,200); public Rectangle itemSize = new Rectangle(0,0,64,64); public Bitmap itemBitmap = null; public string itemName; public string LocateItem(string searchName) { string tItemName = null; //if the item name matches the search parameter, send it up) if (itemName == searchName) { return itemName; } if (subitem != null) { //spiral down a level foreach (Item tSearchItem in subitem) { tItemName = tSearchItem.LocateItem(searchName); if (tItemName != null) break; //exit for if item was found } } //do name logic (use index numbers) //if LocateItem of the subitems returned nothing and the current item is not a match, return null (not found) if (tItemName == null && itemName != searchName) { return null; } //if it's not the item being searched for and the search item was found, change the string and return it up if (tItemName != null && itemName != searchName) { tItemName.Insert(0, itemName + "."); //insert the parent name on the left --> TopItem.SubItem.SubSubItem.SubSubSubItem return tItemName; } //default not found return null; } } My question is if there is an easier way to do this with lists? I've been going back and forth in my head as to whether I should use lists or just an array. The only reason I have a list is so that I don't have to make code to resize the array each time I add or remove an item.

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  • Is there any practical usage of Doubly Linked List, Queues and Stacks?

    - by Chouette
    I've been coding for quite sometime now. And my work pertains to solving real-world business scenarios. However, I have not really come across any practical usage of some of the data structures like the Linked List, Queues and Stacks etc. Not even at the business framework level. Of course, there is the ubiquitous HashTable, ArrayList and of late the List...but is there any practical usage of some of the other basic data structures? It would be great if someone gave a real-world solution where a Doubly Linked List "performs" better than the obvious easily usable counterpart.

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  • Java ORM related question - SQL Vs Google DB (Big Table?) GAE

    - by StackerFlow
    I was wondering about the following two options when one is not using SQL tables but ORM based DBs (Example - when you are using GAE) Would the second option be less efficient? Requirement: There is an object. The object has a collection of similar items. I need to store this object. Example, say the object is a tree and it has a collection of leaves. Option 1: Traditional SQL type structure: Table for the Tree (with TreeId as the identifier for a row in the Table.) Table for the Leaves (where each leaf has a TreeId and to show the leaves of a tree, I query all leaves where the TreeId is the Id of the tree.) Here, the Tree structure DOES NOT have a field with leaves. Option 2: ORM / GAE Tables: Using the same example above, I have an object for Tree where the object has a collection (Set/List in Java/C++) of leaves. I store and retrieve the Tree together with the leaves (as the leaves are implemented as a Set in the Tree object) My question is, will the second one be less efficient that the first option? If so, why? Are there other alternatives? Thank you!

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  • sorting char* arrays

    - by skazhy
    Hi! I have a datastructure struct record { char cont[bufferSize]; record *next; }; When I add new records to this structure, I want them to be sorted alphabetically. I made this function, that adds record in the right place (by alphabet) in the linked list: record *start=NULL, *p, *x; void recAdd(char*temp) { p = new record; temp[strlen(temp)] = '\0'; for (int j=0;j<bufferSize;j++) p->cont[j] = temp[j]; if (start==NULL) start=p; else { x=start; int c=0; while (recComp(x->cont,p->cont) <= 0 && x->next != NULL) { x=x->next; c++; } if (c == 0) { p->next=start; start=p; } else { x=start; for (int i=0;i<c;i++) x=x->next; p->next=x->next; x->next=p; } } for (int j=0;j<bufferSize;j++) temp[j] = NULL; }; But somehow it doesn't sort things right. What is wrong with my function?

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  • How do I learn algorithms and data structures?

    - by sushil bharwani
    this is in continuation to my previous question where i asked is it necessary to learn algorithm and datastructures. I feel yes it is. Now when i work in a enviornment where i wont ever get the chance to learn it by experimenting or practically or in any assignment. What is the right approach like the right books, right kind of problems, right kind of resources that i can go through to give six months or a year or two to learn it. And also mould my mind in a way that it can relate problems to datastructures and algos.

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  • Where to put a glossary of important terms and patterns in documentation?

    - by Tetha
    Greetings. I want to document certain patterns in the code in order to build up a consistent terminology (in order to easen communication about the software). I am, however, unsure, where to define the terms given. In order to get on the same level, an example: I have a code generator. This code generator receives a certain InputStructure from the Parser (yes, the name InputStructure might be less than ideal). This InputStructure is then transformed into various subsequent datastructures (like an abstract description of the validation process). Each of these datastructures can be either transformed into another value of the same datastructure or it can be transformed into the next datastructure. This should sound like Pipes and Filters to some degree. Given this, I call an operation which takes a datastructures and constructs a value of the same datastructure a transformation, while I call an operation which takes a datastructure and produces a different follow-up datastructure a derivation. The final step of deriving a string containing code is called emitting. (So, overall, the codegenerator takes the input-structure and transforms, transforms, derives, transforms, derives and finally emits). I think emphasizing these terms will be benefitial in communications, because then it is easy to talk about things. If you hear "transformation", you know "Ok, I only need to think about these two datastructures", if you hear "emitting", you know "Ok, I only need to know this datastructure and the target language.". However, where do I document these patterns? The current code base uses visitors and offers classes called like ValidatorTransformationBase<ResultType> (or InputStructureTransformationBase<ResultType>, and so one and so on). I do not really want to add the definition of such terms to the interfaces, because in that case, I'd have to repeat myself on each and every interface, which clearly violates DRY. I am considering to emphasize the distinction between Transformations and Derivations by adding further interfaces (I would have to think about a better name for the TransformationBase-classes, but then I could do thinks like ValidatorTransformation extends ValidatorTransformationBase<Validator>, or ValidatorDerivationFromInputStructure extends InputStructureTransformation<Validator>). I also think I should add a custom page to the doxygen documentation already existing, as in "Glossary" or "Architecture Principles", which contains such principles. The only disadvantage of this would be that a contributor will need to find this page in order to actually learn about this. Am I missing possibilities or am I judging something wrong here in your opinion? -- Regards, Tetha

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  • How do I memoize expensive calculations on Django model objects?

    - by David Eyk
    I have several TextField columns on my UserProfile object which contain JSON objects. I've also defined a setter/getter property for each column which encapsulates the logic for serializing and deserializing the JSON into python datastructures. The nature of this data ensures that it will be accessed many times by view and template logic within a single Request. To save on deserialization costs, I would like to memoize the python datastructures on read, invalidating on direct write to the property or save signal from the model object. Where/How do I store the memo? I'm nervous about using instance variables, as I don't understand the magic behind how any particular UserProfile is instantiated by a query. Is __init__ safe to use, or do I need to check the existence of the memo attribute via hasattr() at each read? Here's an example of my current implementation: class UserProfile(Model): text_json = models.TextField(default=text_defaults) @property def text(self): if not hasattr(self, "text_memo"): self.text_memo = None self.text_memo = self.text_memo or simplejson.loads(self.text_json) return self.text_memo @text.setter def text(self, value=None): self.text_memo = None self.text_json = simplejson.dumps(value)

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  • ADO Exception in HQL query

    - by Yoav
    I have 2 classes: Project and DataStructure. Class Project contains member List<DataStructure. My goal is to load a Project and all its DataStructures in one call. public class Project { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual ISet<DataStructure> DataStructures { get { } set { } } } public class DataStructure { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual string Description { get { } set { } } public virtual Project Project { get { } set { } } public virtual IList<DataField> Fields { get { } set { } } } Note that DataStructure also contains a list of class DataField but I don’t want to load these right now. Mapping in Fluent NHibernate: public class ProjectMap : ClassMap<Project> { public ProjectMap() { Table("PROJECTS"); Id(x => x.Pk, "PK"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); HasMany<DataStructure>(x => x.DataStructures).KeyColumn("FK_PROJECT"); } } public class DataStructureMap : ClassMap<DataStructure> { public DataStructureMap() { Table("DATA_STRUCTURES"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); Map(x => x.Description, "DESCRIPTION"); References<Project>(x => x.Project, "FK_PROJECT"); HasMany<DataField>(x => x.Fields).KeyColumn("FK_DATA_STRUCTURE"); } } This is my query: using (ISession session = SessionFactory.OpenSession()) { IQuery query = session.CreateQuery("from Project pr left join pr.DataStructure"); project = query.List<Project>(); } query.List() returns this exception: NHibernate.Exceptions.GenericADOException: Could not execute query[SQL: SQL not available] ---> System.ArgumentException: The value "System.Object[]" is not of type "Project" and cannot be used in this generic collection.

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