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• Where can I learn more about datastructure tricky questions?

  - by Sandbox

  I am relatively new to programming (around 1 year programming C#-winforms). Also, I come from a non CS background (no formal degree) Recently, while being interviewed for a job, I was asked about implementing a queue using a stack. I fumbled and wan't able to answer the question. After, the interview I could do it(had to spend some time). I have learnt (and think that I know it well) basic algorithms in datastructures using the book Data Structures: A Pseudocode Approach with C - Richard F. Gilberg (Author) . I want to know about sites/ books which have such questions along with answers. I think this will allow me to develop my CS specific problem solving skills. Any help is appreciated. BOUNTY: I am looking at some blog/website with datastructure and algorithms Q&A.

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• Comment out a python code block

  - by gbarry

  Is there any mechanism to comment out large blocks of Python code? Right now the only ways I can see of commenting out code are to either start every line with a #, or to enclose the code in """ (triple quotes), except that actually makes it show up in various doc tools. Edit--After reading the answers (and referring to the "duplicate"), I have concluded the correct answer is "No". One person said so, and the rest lectured us about editors. Not a bad thing, but I feel it's important to put the answer at the top.

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• Does importing of packages change visibility of classes?

  - by Roman

  I jsut learned that A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package. This is a clear statement. But this information interfere with my understanding of importing of packages (which easily can be wrong). I thought that importing a package I make classes from the imported package visible to the importing class. So, how does it work? Are public classes visible to all classes everywhere under condition that the package containing the public class is imported? Or there is not such a condition? What about the package-private classes? They are invisible no mater if the containing package was imported or not? ADDED: It seems to me that I got 2 answers which are marked as good (up-voted) and which contradict eachother.

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• How to do GUI for bash scripts?

  - by maxorq

  I want to do some graphic dialogs for my script but don't know how. I hear something about GTK-Server or something like that. If someone know how to link bash with tcl/tk I also be satisfied. Please do not post something like "change to C++" because my project must be a script in BASH, there are no other option. Any ideas? P.S. Sorry for bad english! EDIT: Thanks for answers but I don't want "graphics" like colors in console, but windows that shows like hmmmm..... net browser which I can move, minimalize etc. I will test xmessage, but I don't think that will be that what I searching for. EDIT2: And one more thing. I don't want make a simple dialog like yes/no, but some interface like progress bars and buttons, something like game :)

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• Does style="color: #FFF;" render as #F0F0F0 or #FFFFFF?

  - by Dolph Mathews

  When defining colors using "shorthand hexidecimal" (style="color: #FFF;"), is there a defined method for expanding the shorthand? (style="color: #F0F0F0;" or style="color: #FFFFFF;") Do all browsers use the same expansion method? Is this behavior by specification (if so, where is it defined)? Does the expansion method perhaps vary between CSS 1/2/3? I've observed that "most browsers" expand to #FFFFFF. Are there any other places where this shorthand notation is allowed, but the expansion method is different? I've always avoided using shorthand hex, because I've never known the answers to these questions...

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• Measuring the performance of classification algorithm

  - by Silver Dragon

  I've got a classification problem in my hand, which I'd like to address with a machine learning algorithm ( Bayes, or Markovian probably, the question is independent on the classifier to be used). Given a number of training instances, I'm looking for a way to measure the performance of an implemented classificator, with taking data overfitting problem into account. That is: given N[1..100] training samples, if I run the training algorithm on every one of the samples, and use this very same samples to measure fitness, it might stuck into a data overfitting problem -the classifier will know the exact answers for the training instances, without having much predictive power, rendering the fitness results useless. An obvious solution would be seperating the hand-tagged samples into training, and test samples; and I'd like to learn about methods selecting the statistically significant samples for training. White papers, book pointers, and PDFs much appreciated!

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• Monitoring Reasoning Progress using the Pellet Reasoner

  - by Nico

  I am currently constructing an OWL ontology, which - until very recently classified rapidly using the Pellet reasoner. However, since the introduction of several new classes, the reasoning performance has slowed to a crawl. Although the reasoner completes and the ontology does not contain any unsatisfiable concepts etc, the time the reasoning takes is unacceptable. I am currently trying to track down the offending classes/class that may have led to the slowdown. Here's my question: is it possible to log the reasoning progreess of Pellet? I.e. is it possible to produce some output that will document how long pellet has spent on certain reasoning tasks/traces how long reasoning over any given class and axiom takes? If so, does anyone have some java code they could post up? Thanks in advance for your answers!

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• iPhone: How to Determine Average Light/Dark of an Area of an UIImage

  - by TechZen

  I need to place labels with a transparent background over a variable-content UIImage. Readability will vary significantly depending on the relationship between the color of the label's text and the color/luminosity of the area of the image displayed under the label. Since the image will be constantly changing, the color of the label's text needs to change in sync. I have found several techniques for determining the color, perceived luminosity etc of a single pixel. However, I need to rather quickly (while a view loads) determine the rough perceived color/luminosity of an area of the UIImage under the frame of the UILabel. I presume I will also need to measure the alpha because the same color/luminosity looks different at different alpha values. Is there a way to calculate such a value for an area? Will I be reduced to simply summing pixels? If it comes to that, is there an algorithm to accomplish this? I've thought of two possible approaches: Perform some "folding" operations i.e. combining pixels from one half of the area to the other half. Then repeat until I get a single value. Would this be practical? How would you logically combine pixels to average their perceived color/luminosity? Sample a statistically significant number of pixels in the area and then combine them (somehow) to get a rough measure. I think this problem comes up a lot these days with people being so found of customizing backgrounds. Seems like something that would be worth my time to bang out a category or class to handle this and then share it around.

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• oralce + java encoding problem while insert

  - by Ahmad

  hi, I am kind of stuck on this one. im not a java or oracle guru, so please give detailed answers :) i've a web-service that inserts something into DB. the web-service is hosted on axis. the db is oracle with following properties: NLS_LANGUAGE AMERICAN NLS_TERRITORY AMERICA NLS_CHARACTERSET ZHS16GBK the web-service is hosted on windows server 2008, english version but i have changed the locale of the system to chinese now the data after insert has encoding problem and shows strange characters like ????,exxk?? the jws file has GBK encoding. and the data that is inserted into the DB is hard-coded in the file [we are not reading it from REQUEST]

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• C# listbox,params

  - by Oyeme

  As Andrew Hare suggested in his answer: Create a field to store all the ListBox instances and then change the constructor to accept an arbitrary number of them: by I tried the following class scaner { readonly IEnumerable<ListBox> listBoxes; public IEnumerable<ListBox> ListBoxes { get { return this.listBoxes; } } public scaner(params ListBox[] listBoxes) { this.listBoxes = listBoxes; } } This will allow you to do this: scaner Comp = new scaner(listBox1, listBox2); How can i access listbox1? In class scaner i'm trying to call this.listBoxes. (I need to call the listbox1 in scaner class.How can i do/call it? Thanks for answers.

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• prevent hover set by the CSS

  - by meo

  I try to prevent the Browser from using the :hover effect of the CSS. $("ul#mainFilter a").hover( function(o){ o.preventDefault(); ...do my stuff... }, function(o){ o.preventDefault(); ...do my stuff... }); I tired it with return false; to but it does not work. Does anyone know how to do this? due the answers i give you some more nfo: I have set the a and a:hover styles, in my CSS already. Now if JS is available on the clients machine, i want to overwrite the effect with a smoother one. (using jQuery color plugin) As mentioned by fudgey, a work around would be to set the style (using .css()) but i would have to overwrite every single effect specified in the CSS (see here: http://jsfiddle.net/raPeX/1/ ). I am looking for a generic solution.

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• JQuery:FullCalendar Plugin: Events are not shown in week view and day view but are shown in month vi

  - by bocode

  I've the following code to fetch events: $('#calendar').fullCalendar({ theme: true, slotMinutes: 10, header: { left: 'prev,next today', center: 'title', right: 'month,agendaWeek,agendaDay', }, defaultView: 'agendaDay', allDaySlot: false, editable: false, events: "/cgi-bin/shlk/getshlkruns.pl" }); The output from getshlkruns.pl is fairly simple json feed: [{'title': 'Successful','start': 1266398223,'end': 1266398266,'url': '/shlk/cgi-bin/getshlkrunlog.pl?i=21'}] There are several events like above (i've removed for brevity sake). So the above events show up when am in the month view but mysteriously absent when am in week or day view. What am doing wrong here? Thanks in advance for your answers.

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• Rails Nested Attributes, Relationship for Shared or Common Object

  - by SooDesuNe

  This has to be a common problem, so I'm surprised that Google didn't turn up more answers. I'm working on a rails app that has several different kinds of entities, those entities by need a relation to a different entity. For example: Address: a Model that stores the details of a street address (this is my shared entity) PersonContact: a Model that includes things like home phone, cell phone and email address. This model needs to have an address associated with it DogContact: Obviously, if you want to contact a dog, you have to go to where it lives. So, PersonContact and DogContact should have foreign keys to Address. Even, though they are really the "owning" object of Address. This would be fine, except that accepts_nested_attributes_for is counting on the foreign key being in Address to work correctly. What's the correct strategy to keep the foreign key in Address, but have PersonContact and DogContact be the owning objects?

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• Tutorial/resource for implementing VM

  - by zaharpopov

  Hello, I want self-education purpose implement a simple virtual machine for a dynamic language, prefer in C language. Something like the Lua VM, or Parrot, or Python VM, but simpler. Are there any good resources/tutorials on achieving this, apart from looking at code and design documentations of the existing VMs? Thanks in advance for your answers and ideas Edit: why close vote? I don't understand - is this not programming. Please comment if there is specific problem with my question.

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• Optional attribute values in MappedField

  - by David Brooks

  I'm new to Scala and Lift, coming from a slightly odd background in PLT Scheme. I've done a quick search on this topic and found lots of questions but no answers. I'm probably looking in the wrong place. I've been working my way through tutorials on using Mapper to create database-backed objects, and I've hit a stumbling block: what types should be used to stored optional attribute values. For example, a simple ToDo object might comprise a title and an optional deadline (e.g. http://rememberthemilk.com). The former would be a MappedString, but the latter could not be a MappedDateTime since the type constraints on the field require, say, defaultValue to return a Date (rather than a Date or null/false/???). Is an underlying NULL handled by the MappedField subclasses? Or are there optional equivalents to things like MappedInt, MappedString, MappedDateTime that allow the value to be NULL in the database? Or am I approaching this in the wrong way?

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• How do I measure distances in an image?

  - by Ram Bhat

  Let's say we have an image like so Let's say we've already used filters and an edge detection algorithm in this pic. Now my goal is to measure distances (NOT actual distances, distance can be in any arbitrary unit) . eg: How do I find the length of the hall? (until the window) Or the height of the bookshelves? How exactly do you place the "scale" and measure. I'm looking for ideas. However it would help if the answers were in terms of OpenCV.

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• Creating a global variable on the fly. [PHP ENCRYPTION]

  - by stormdrain

  Is there a way to dynamically create constant variables on the fly? The idea is that upon logging into the system, a user would be asked to upload a small text file that would be fread, and assigned to a var that would be accessible throughout the system. If this is possible, just to be clear, would this variable then only be accessible to that user and only while the session is alive? Security being the main concern here, would it be more practical to store the var in a session variable? The plan: Data in the db will be encrypted via mcrypt, and the key will be stored on USB thumbdrives. The user will insert the thumbdrive when going to access the system. Upon logging in, the app will prompt the user to upload the key. They will navigate to the thumbdrive and key. Via fopen and fread, the key will be assigned to a global var which will then allow access to encrypted data, and will be used to encrypt new info being entered to the db. When the user logs out, or session times out, the global var will become empty. Thanks!

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• apache tomcat 8 websocket origin and client address

  - by user2926082

  i hope someone can help me ... i am using apache tomcat 8.0.0-RC5 and JSR-356 web socket API ... I have 2 questions: 1) Is it possible to get the client ip on @OnOpen method ?? 2) Is it possible to get the origin of the connection ??? I followed the websocket example which comes with the distribution of tomcat and i was not able to find the answers .... My java class is basically as follow @ServerEndpoint(value = "/data.socket") public class MyWebSocket { @OnOpen public void onOpen(Session session) { // Here is where i need the origin and remote client address } @OnClose public void onClose() { // disconnection handling } @OnMessage public void onMessage(String message) { // message handling } @OnError public void onError(Session session, Throwable throwable) { // Error handling } }

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• PHP registration script: verifying and telling the user what went wrong

  - by Maxime

  Hi, I'm building a registration script and I want to insert the user's input (username, mail) ONLY if it's not already in the database. What I usually do in such cases is a request to see if something's already there, something like: "SELECT * FROM things WHERE thing_name = '$treated_user_input'". I have two fields that need to be unique this time though. Is there a way to do only one SELECT request and still be able to tell the user exactly what field went wrong? Or do I have to do one request per unique field? Thanks for your answers.

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• Sending variables in URLs in PHP with echo

  - by alexpelan

  Hi all, I can't really find good guidelines through google searches of the proper way to escape variables in URLs. Basically I am printing out a bunch of results from a mysql query in a table and I want one of the entries in each row to be a link to that result's page. I think this is easy, that I'm just missing a apostrophe or backslash somewhere, but I can't figure it out. Here's the line that's causing the error: echo "<a href = \"movies.php/?movie_id='$row['movie_id']'\"> Who Owns It? </a> "; and this is the error I'm getting: Parse error: syntax error, unexpected T_ENCAPSED_AND_WHITESPACE, expecting T_STRING or T_VARIABLE or T_NUM_STRING If you could elaborate in your answers about general guidelines for working with echo and variables in urls, that would be great. Thanks.

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• jQuery Ajax Methods Not Returning XHR Object

  - by Nate

  UPDATE: I haven't figured out what's going on, but this definitely seems to be a problem with my project. After creating a simple test page, I was able to verify that getJSON does in fact return an XHR object like it's supposed to. Per the stackoverflow question/answer here: Kill ajax requests using javascript using jquery. and a number of other question/answers on this site and others, the jQuery Ajax methods should return the XHR object. However, when I run the following code, request is "undefined". var request = $.getJSON(url, function(data) { console.log(data); }); console.log(request); Did I miss a change in jQuery? I'm using 1.4.4.

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• Need help configuring IIS 5.1 on XP

  - by S Bogdan

  Hello everybody. Fist of all I want to say IIS to me is like a vending machine to a monkey. So I have Windows XP SP2 with IIS 5.1 on it and an ASP.NET Web Forms project. I just want my website to be accessed by someone else from the internet or from my local network. How do I configure IIS so that is possible? I tried a lot of user guides, but I don't know what I did wrong cause all I got was Page not foud and Service Unavailable. Thanks in advance for all your guidance and answers.

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• Unable to implement JMS using ApacheMQ

  - by Galaxin

  Iam trying to implement a simple JMS code in eclipse using ApacheMQ. I have downloaded the ApacheMQ from apache.org and sample JMS sender from SimpleQueueSender and receiver from SimpleQueueReceiver respectively. Now how should i execute this code? I have already gone through all related tutorials but couldnot find answers to these questions. Please suggest solutions on What all are the changes to be done regarding classpaths,settings after the activemq is started as below INFO | jetty-7.1.6.v20100715 INFO | ActiveMQ WebConsole initialized. INFO | Initializing Spring FrameworkServlet 'dispatcher' INFO | ActiveMQ Console at http://0.0.0.0:8161/admin INFO | ActiveMQ Web Demos at http://0.0.0.0:8161/demo INFO | RESTful file access application at http://0.0.0.0:8161/fileserver INFO | Started [email protected]:8161 how to proceed next? 2.Should this server be added in the eclipse as a new server and then the program is run on that server? 3.Can these programs be run from eclipse or should they executed from a separate console?

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• How to write this snippet in Python?

  - by morpheous

  I am learning Python (I have a C/C++ background). I need to write something practical in Python though, whilst learning. I have the following pseudocode (my first attempt at writing a Python script, since reading about Python yesterday). Hopefully, the snippet details the logic of what I want to do. BTW I am using python 2.6 on Ubuntu Karmic. Assume the script is invoked as: script_name.py directory_path import csv, sys, os, glob # Can I declare that the function accepts a dictionary as first arg? def getItemValue(item, key, defval) return !item.haskey(key) ? defval : item[key] dirname = sys.argv[1] # declare some default values here weight, is_male, default_city_id = 100, true, 1 # fetch some data from a database table into a nested dictionary, indexed by a string curr_dict = load_dict_from_db('foo') #iterate through all the files matching *.csv in the specified folder for infile in glob.glob( os.path.join(dirname, '*.csv') ): #get the file name (without the '.csv' extension) code = infile[0:-4] # open file, and iterate through the rows of the current file (a CSV file) f = open(infile, 'rt') try: reader = csv.reader(f) for row in reader: #lookup the id for the code in the dictionary id = curr_dict[code]['id'] name = row['name'] address1 = row['address1'] address2 = row['address2'] city_id = getItemValue(row, 'city_id', default_city_id) # insert row to database table finally: f.close() I have the following questions: Is the code written in a Pythonic enough way (is there a better way of implementing it)? Given a table with a schema like shown below, how may I write a Python function that fetches data from the table and returns is in a dictionary indexed by string (name). How can I insert the row data into the table (actually I would like to use a transaction if possible, and commit just before the file is closed) Table schema: create table demo (id int, name varchar(32), weight float, city_id int); BTW, my backend database is postgreSQL

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• How web apps ask location of mobile device?

  - by kikkoman90

  Hello, Many modern mobile phones (google nexus one etc.) have some kind of built in location service. when i go to a some website (eg. google.com) that website asks if I'm willing to share my location with that site. How do you actually ask for mobile device to give out it's location to the site? And in what format is that location given? I've got no clue and didn't find any answers from google, neither.

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