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• Implementation of a distance matrix of a binary tree that is given in the adjacency-list representation

  - by Denise Giubilei

  Given this problem I need an O(n²) implementation of this algorithm: "Let v be an arbitrary leaf in a binary tree T, and w be the only vertex connected to v. If we remove v, we are left with a smaller tree T'. The distance between v and any vertex u in T' is 1 plus the distance between w and u." This is a problem and solution of a Manber's exercise (Exercise 5.12 from U. Manber, Algorithms: A Creative Approach, Addison-Wesley (1989).). The thing is that I can't deal properly with the adjacency-list representation so that the implementation of this algorithm results in a real O(n²) complexity. Any ideas of how the implementation should be? Thanks.

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• Should I create subclass NSManagedObject or not?

  - by TP

  Hi, I have spent a few days learning and writing NSCoding and finally got it working. However, it took very long to archive and unarchive the (quite complex) object graph, which is unacceptable. After searching the internet for some time, I think the better way is to use core data. Do you recommend that 1) I should rewrite all my classes as subclasses of NSManagedObject or 2) should I create an instance variable of NSManagedObject in each of my class so that any changes to the class also updates its core data representation? Doing either way will need significant changes to the exiting classes and I think I have to update lots of unit test cases as well if it changes the way the classes are initialized. What do you recommend? I really don't want to head to the wrong approach again... Thanks!

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• Allowing developer-specific settings in VS2008 projects

  - by Xavier Nodet

  Is it possible to combine the following properties, and if so, how? Store in our version control system some Visual Studio 2008 native C++ project files for the developers in our team that use this IDE. Allow some of those developers to tweak their projects (e.g. using debug version of third-party libraries instead of the usual ones). Make sure these modifications are done in files that are not versioned. In other words, I would like to allow developers to tweak some settings in their projects without risking that these changes are committed. An 'optional VSPROP' file approach seems doomed to fail, as VS2008 refuses to load projects that refer to non-existent VSPROP files... Any other suggestion? Is this possible with VS2010?

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• Most efficient way for a lookup/search in a huge list (python)

  - by user229269

  Hey guys, -- I just parsed a big file and I created a list containing 42.000 strings/words. I want to query [against this list] to check if a given word/string belongs to it. So my question is: What is the most efficient way for such a lookup? A first approach is to sort the list [list.sort()] and then just use the if word in list: print 'word' -- which is really trivial and I am sure there is a better way to do it. My goal is to apply a fast lookup that finds whether a given string is in this list or not. If you have any ideas of another data structure, they are welcome. Yet, I want to avoid for now more sophisticated data-structures like Tries etc. I am interested in hearing ideas (or tricks) about fast lookups or any other python library methods that might do the search faster than the simple 'in'. Thanks in advance!

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• Use google analytics custom events for feedback form.

  - by chacko

  I was thinking of having a simple feedback form in my website. It would be something like: Your Feedback will help us improve. [ ] and then a textfield/textarea where the user can type (let's say) up to 100 characters of feedback. Rather than handling it all myself on the serverside I was thinking to use google analytics (since my site is already wireup) and everytime a user writes a comment send a custom event to google analytics. I think it might work. Can people suggest a better approach or point out any problem with this idea thanks

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• Zend Framework: isValid() clears values from disabled form fields!

  - by Andrew

  When you submit a form, disabled form fields are not submitted in the request. So if your form has a disabled form field, it makes working with Zend_Form::isValid() a little frustrating. $form->populate($originalData); $form->my_text_field->disabled = 'disabled'; if (!$form->isValid($_POST)) { //form is not valid //since my_text_field is disabled, it doesn't get submitted in the request //isValid() will clear the disabled field value, so now we have to re-populate the field $form->my_text_field->value($originalData['my_text_field']); $this->view->form = $form; return; } // if the form is valid, and we call $form->getValues() to save the data, our disabled field value has been cleared! Without having to re-populate the form, and create duplicate lines of code, what is the best way to approach this problem?

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• erlang io:format, and a hanging web application

  - by williamstw

  While I'm learning a new language, I'll typically put lots of silly println's to see what values are where at specific times. It usually suffices because the languages typically have available a tostring equivalent. In trying that same approach with erlang, my webapp just "hangs" when there's a value attempted to be printed that's not a list. This happens when variable being printed is a tuple instead of a list. There's no error, exception, nothing... just doesn't respond. Now, I'm muddling through by being careful about what I'm writing out and as I learn more, things are getting better. But I wonder, is there a way to more reliably to [blindly] print a value to stdout? Thanks, --tim

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• How to make django test framework read from live database?

  - by lfborjas

  I realize there's a similar question here, but this one has a different approach: I have a django app that does queries over data indexed with djapian ; I'd like to write unit tests for this app's search component, and, obviously, I'd need the django settings module and all connections with the database active, so the test runner that django provides seems ideal. however, the django testing framework creates a dummy database and I'd hate to dump all my data to a fixture and then index it (the tests would take forever!); My data isn't at risk because the tests would only read from the database, so, how could this be achieved? -I'm new at this whole unit testing thing, so the solution of writing a new test runner I read in that similar question doesn't enlighten me a bit, at least not without some details

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• Level editor for 3D games with open format or API?

  - by furtelwart

  I would like to experiment with machine generated levels for a 3D game. I'm very open which game this will be. I just like the idea to run through a generated map. For this approach, it would be great if I can use an API or an open format for level designs. Is there an open source level system that can be used in several game engines (ego shooter or whatever)? I don't know if I explained my point clearly, so please add a comment with your question. I will try to clearify my point.

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• How can i have different LINQ to XML quries based on two different condition?

  - by Subhen

  Hi , We want the query result should be assigned with two results based on some condition like following: var vAudioData = (from xAudioinfo in xResponse.Descendants(ns + "DIDL-Lite").Elements(ns + "item") if((xAudioinfo.Element(upnp + "artist")!=null) { select new RMSMedia { strAudioTitle = ((string)xAudioinfo.Element(dc + "title")).Trim() }; } else select new RMSMedia { strGen = ((string)xAudioinfo.Element(dc + "Gen")).Trim() }; The VarAudioData should contain both if and else condition values. I have added the if condition just to project , what is my needs, m quite sure though that we can not use if and else. Please help if there are any other approach to accomplish this. Thanks, Subhen

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• Using a locale-dependent sorting function in Ruby/Rails

  - by knuton

  What is a good approach to sorting an array of strings in accordance with the current locale? For example the standard Array#sort puts "Ä" after "Z", which is not correct in German. I would have expected the gem I18n to offer a hook for defining my own sorting algorithms or providing collation strings or objects. In my imagination, passing this proc or string to the sort function, would make it behave as necessary. I know that this is possible in Python, for example. Google has not helped me this time. Can you? Any advice appreciated!

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• Searching algorithmics: Parsing and processing a request

  - by James P.

  Say you were to create a search engine that can accept a query statement under the form of a String. The statement can be used to retrieve different types of objects with a given set of characteristics and possibly linked to other objects. In plain english or pseudo-code using an OOP approach, how would you go about parsing and processing statements as follows to get the series of desired objects ? get fruit with colour green get variety of apples, pears from Andy get strawberry with colour "deep red" and origin not Spain get total of sales of melons between 2010-10-10 and 2010-12-30 get last deliverydate of bananas from "Pete" and state not sold Hope the question is clear. If not I'll be more than happy to reformulate. P.S: This isn't homework ;)

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• More elegant way to parse inline variables in strings

  - by Tom

  Currently I have this: function parse_string($string, $variables){ extract($variables); return eval('return "'. addcslashes($string, '"') .'";'); } So I can input this string: 'Hi {$name}, my name is {$own_name}' Together with this array: array('name' => 'John', 'own_name' => 'Tom') And get this back: 'Hi John, my name is Tom'   I've never liked this eval() approach but it works and it's fast (faster than regex at least). Question: Is there a more elegant way to do this (faster than using regex) in PHP5?

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• Ref to map vs. map to refs vs. multiple refs

  - by mikera

  I'm working on a GUI application in Swing+Clojure that requires various mutable pieces of data (e.g. scroll position, user data, filename, selected tool options etc.). I can see at least three different ways of handling this set of data: Create a ref to a map of all the data: (def data (ref { :filename "filename.xml" :scroll [0 0] })) Create a map of refs to the individual data elements: (def datamap { :filename (ref "filename.xml") :scroll (ref [0 0]) })) Create a separate ref for each in the namespace: (def scroll (ref [0 0])) (def filename (ref "filename.xml")) Note: This data will be accessed concurrently, e.g. by background processing threads or the Swing event handling thread. However there probably isn't a need for consistent transactional updates of multiple elements. What would be your recommended approach and why?

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• sqlalchemy: what is the difference between declaring the cascade within the foreign key vs relation?

  - by steve

  what is the difference between declaring the cascade within a foreign key vs relations? class Contact(Base): __tablename__ = 'contacts' id = Column(Integer, primary_key=True) addresses = relation("Address", backref="contact") class Address(Base): __tablename__ = 'addresses' id = Column(Integer, primary_key=True) contact_id = Column(Integer, ForeignKey('contact.id', onupdate="CASCADE", ondelete="CASCADE"))) vs class Contact(Base): __tablename__ = 'contacts' id = Column(Integer, primary_key=True) addresses = relation("Address", backref="contact", cascade="all, delete-orphan") class Address(Base): __tablename__ = 'addresses' id = Column(Integer, primary_key=True) contact_id = Column(Integer, ForeignKey('contact.id')) with the foreign key declaration, it seems like the cascade is enforced at the database level. how does the relations approach work? thanks!

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• Good code visualization / refactoring tools for C++?

  - by Paul D.

  I've found myself coming across a lot of reasonably large, complicated codebases at work recently which I've been asked to either review or refactor or both. This can be extremely time consuming when the code is highly concurrent, makes heavy use of templates (particularly static polymorphism) and has logic that depends on callbacks/signals/condition variables/etc. Are there any good visualization tools for C++ period, and of those are there any that actually play well with "advanced" C++ features? Anything would probably be better than my approach now, which is basically pen+paper or stepping through the debugger. The debugger method can be good for following a particular code path, but isn't great for seeing the big picture you really need when doing serious refactoring. EDIT: I should mention that Visual Studio plugins aren't going to be a lot of help to me, since our stuff is mostly Linux-only.

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• SQL query: how to translate IN() into a JOIN?

  - by tangens

  I have a lot of SQL queries like this: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o WHERE o.Id IN ( SELECT DISTINCT Id FROM table1, table2, table3 WHERE ... ) These queries have to run on different database engines (MySql, Oracle, DB2, MS-Sql, Hypersonic), so I can only use common SQL syntax. Here I read, that with MySql the IN statement isn't optimized and it's really slow, so I want to switch this into a JOIN. I tried: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o, table2, table3 WHERE ... But this does not take into account the DISTINCT keyword. Question: How do I get rid of the duplicate rows using the JOIN approach?

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• Identify the checkbox that is checked

  - by lucky

  Hello Everyone, I have 2 checkboxes in a form and onclick of these, some php code needs to be executed and based on the result of the code, the checkbox is checked or unchecked. So i have written onclick = document.formName.submit(); Now it is triggering the same page and i am able to write the code. I am not able to differentiate which checkbox is checked. I don't want to use the procedure of:- calling javascript and then storing the value of the checkbox in a variable and making this variable as invisible. I would like to write something like document.formName.submit('checkbox1'). So that i should be able to handle the value of this or i dont know. Please suggest me an alternative method or better approach.

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• Show friendly message on ASP.NET Ajax error

  - by balexandre

  You all know how annoying is this: I do have a log system and the correct error is well explicit there, but I want to give a better message to the user. I keep trying several ways but I'm using Telerik components and well jQuery and I ended up using both ASP.NET Ajax methods and jQuery, so I use function pageLoad() { try { var manager = Sys.WebForms.PageRequestManager.getInstance(); manager.add_endRequest(endRequest); manager.add_beginRequest(OnBeginRequest); manager } catch (err) { alert(err); } } as well $(document).ready(function() { ... } that alert(err) is never fired even upon OnClick events what's the best approach to avoid this message errors and provide a cleaner way? all this happens in <asp:UpdatePanel> as I use that when I didn't know better (3 years ago!) and I really don't want to mess up and build all again from scratch :( Any help is greatly appreciated Updated with more error windows after volpav solution

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• Retrieving data from database. Retrieve only when needed or get everything?

  - by RHaguiuda

  I have a simple application to store Contacts. This application uses a simple relational database to store Contact information, like Name, Address and other data fields. While designing it, I question came to my mind: When designing programs that uses databases, should I retrieve all database records and store them in objects in my program, so I have a very fast performance or I should always gather data only when required? Of course, retrieving all data can only be done if it`s not too many, but do you use this approach when you make sure that the database will be small (< 300 records for example)? I have designed once a similar application that fetches data only when needed, but that was slow (using a Access database). Thanks for all help.

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• How to get all n sets of three consecutives elements in an array or arraylist with a for statement ?

  - by newba

  Hi, I'm trying to do a convex hull approach and the little problem is that I need to get all sets of three consecutive vertices, like this: private void isConvexHull(Ponto[] points) { Arrays.sort(points); for (int i = 0; i <points.length; i++) { isClockWise(points[i],points[i+1],points[i+2]); } //... } I always do something that I don't consider clean code. Could please help me find one or more ways to this? I want it to be circular, i.e., if my fisrt point of the a set is the last element in the array, the 2nd element will be the 3rd in the list and the 3rd in that set will be the the 2nd element in the list, and so on. They must be consecutive, that's all.

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• Fading transition slideshow

  - by Simon Carlson

  I've got a JavaScript that produces a slideshow. It loads the pictures before starting the actual slideshow. Code below. var image1=new Image() image1.src="filename1.jpg" var image2=new Image() image2.src="filename2.jpg" var image3=new Image() image3.src="filename3.jpg" var step=1 function slideit(){ if (!document.images) return document.images.slide.src=eval("image"+step+".src") if (step<3) step++ else step=1 setTimeout("slideit()",1000) } And this is the required HTML for it to work: <img src="filename1.jpg" name="slide" /> Now, if I want to have fading transitions instead of just having new pictures popping up, how do I approach this? By fading I mean either have the old picture fade out, the new fade in or possibly and most likely both fade in/out. Can this be achieved with pure JavaScript and no jQuery or Ajax?

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• How do I render a partial to a string from within a filter attached to a controller

  - by Tristan Havelick

  I have some code I need to use in multiple controllers in a rails 1.0 application (I can't, for strange reasons upgrade to a newer rails). I've extracted the relevant code into a filer object, and I'm using the around_filter construct to execute it. Before the extract, I was using the method render_to_string() to get the contents of a rendered partial into a string. However, this method is protected, so I am unable to access it from within my Filter object. As a workaround, I tried adding this to my ApplicationController: def render_to_string(*a) super(*a) end this seems to have remedied the protection level issue, but now I get the error: Can only render or redirect once per action When no such error occurred before the extraction. Why? Is there a different approach I should take here?

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• ADO.NET Data Service -- non .NET consumers

  - by SwampyFox

  Has anyone come across an example of a non .Net consumer of an ADO.NET Data Service? I am on the second day of looking at what Astoria is and how it can be used. I am also trying to answer why would I use this instead of a web service? After getting my examples running, I kind get the RESTful approach to getting data out the system. And, plugging it into a .net client is incredibly easy. But, then I wondered how a non-.NET consumer would go about it. Any ideas (pointers) definitely appreciated...

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• What is your favorite way to read XML files?

  - by stacker

  Let's take this xml structure as example: <?xml version="1.0" encoding="utf-8"?> <Configuration-content> <XFile Name="file name 1" /> <XFile Name="name2" /> <XFile Name="name3" /> <XFile Name="name4" /> </Configuration-content> C# interface to implement: public class Configuration { public XFile[] Files { get; set; } } public interface IConfigurationRipository { Configuration Get(); void Save(Configuration entity); } I wonder what's the best way to do that. The task is to implement IConfigurationRipository using your favorite approach.

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