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• Data Structures

  - by Phoenix

  There is a large stream of numbers coming in such as 5 6 7 2 3 1 2 3 .. What kind of data structure is suitable for this problem given the constraints that elements must be inserted in descending order and duplicates should be eliminated. I am not looking for any code just ideas? I was thinking of a Self-Balancing BST where we could add the condition that all nodes < current node on left and all nodes current node on right, this takes care of the duplicates .. but i don't think they are necessarily inserted in descending order. Any ideas what might be a better choice .. ofcourse it needs to be efficient time and space wise.

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• Bulk email sender and list management API

  - by goombaloon

  I'm looking for a way to programmatically manage email lists and send large numbers of emails to these lists. The general idea would be similar to how social networking sites send email notifications when a friend posts new content. Since a user could have tens of thousands of followers, it doesn't seem realistic to send these directly from my application so I'm curious if there's a good way to handle this through a service provider. My company is using Google apps but I'm not an expert on their API. Our environment is ASP.NET MVC. Any advice is most appreciated!

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• How to program a neural network for chess?

  - by marco92w

  Hello! I want to program a chess engine which learns to make good moves and win against other players. I've already coded a representation of the chess board and a function which outputs all possible moves. So I only need an evaluation function which says how good a given situation of the board is. Therefore, I would like to use an artificial neural network which should then evaluate a given position. The output should be a numerical value. The higher the value is, the better is the position for the white player. My approach is to build a network of 385 neurons: There are six unique chess pieces and 64 fields on the board. So for every field we take 6 neurons (1 for every piece). If there is a white piece, the input value is 1. If there is a black piece, the value is -1. And if there is no piece of that sort on that field, the value is 0. In addition to that there should be 1 neuron for the player to move. If it is White's turn, the input value is 1 and if it's Black's turn, the value is -1. I think that configuration of the neural network is quite good. But the main part is missing: How can I implement this neural network into a coding language (e.g. Delphi)? I think the weights for each neuron should be the same in the beginning. Depending on the result of a match, the weights should then be adjusted. But how? I think I should let 2 computer players (both using my engine) play against each other. If White wins, Black gets the feedback that its weights aren't good. So it would be great if you could help me implementing the neural network into a coding language (best would be Delphi, otherwise pseudo-code). Thanks in advance!

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• How do you draw like a Crayon?

  - by Simucal

  Crayon Physics Deluxe is a commercial game that came out recently. Watch the video on the main link to get an idea of what I'm talking about. It allows you to draw shapes and have them react with proper physics. The goal is to move a ball to a star across the screen using contraptions and shapes you build. While the game is basically a wrapper for the popular Box2D Physics Engine, it does have one feature that I'm curious about how it is implemented. Its drawing looks very much like a Crayon. You can see the texture of the crayon and as it draws it varies in thickness and darkness just like an actual crayon drawing would look like. The background texture is freely available here. Close up of crayon drawing - Note the varying darkness What kind of algorithm would be used to render those lines in a way that looks like a Crayon? Is it a simple texture applied with a random thickness and darkness or is there something more going on?

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• Object Oriented Design Questions

  - by Robert

  Hello there. I am going to develop a Tic-Tac-Toe game using Java(or maybe other OO Languages).Now I have a picture in my mind about the general design. Interface: Player ,then I will be able to implement a couple of Player classes,based on how I want the opponent to be,for example,random player,intelligent player. Classes: Board class,with a two-dimensional array of integers,0 indicates open,1 indicates me,-1 indicates opponent.The evaluation function will be in here as well,to return the next best move based on the current board arrangement and whose turn it is. Refree class,which will create instance of the Board and two player instances,then get the game begin. This is a rough idea of my OO design,could anybody give me any critiques please,I find this is really beneficial,thank you very much.

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• [C#] Is variable assignment and reading atomic operation (threading)

  - by AStrangerGuy

  I was unable to find any reference to this in the documentations... Is assigning to a double (or any other simple type, including boolean) an atomic operation viewed from the perspective of threads? double value = 0; public void First() { while(true) { value = (new Random()).NextDouble(); } } public void Second() { while(true) { Console.WriteLine(value); } } In this code sample, first method is called in one thread, and the second in another. Can the second method get a messed up value if it gets its execution during assignment to the variable in another thread? I don't care if I recieve the old value, it's only important to receive a valid value (not one where 2 out of 8 bytes are set). I know it's a stupid question, but I want to be sure, cause I don't know how CLR actually sets the variables. Thanks

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• Switching from ListView to VirtualStringTree

  - by Jeff

  Hey S.O! I am trying to build my projects with a VirtualStringTree rather than a Listview, because of the vast speed difference. The thing is, even after looking thru the demo's, I just can't figure out exactly how I would use it as a ListView. Like, adding, deleting, and basically just working with ListView items is so easy, but when I look at the VT, it gets almost too complicated. All I am looking for, is a VT that looks like a ListView, with subitems etc. Here are some routines using the ListView, that I would like to use with VT (This is just a pseudo example: procedure Add; begin with ListView.Items.Add do Begin Caption := EditCaption.Text; SubItems.Add(EditSubItem.Text): End; end; Procedure ReadItem(I : Integer); begin ShowMessage(ListView.Items[I].Caption); ShowMessage(ListView.Items[I].SubItems[0]); end; Of course, also the Delete function, but since thats like 1 line, I didnt bother :P Could anyone maybe translate the above examples into using a ListView style VT? Thanks!

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• NETCF - Optimized Repaint (onPaint)

  - by Nullstr1ng

  Hi Guys, I want to ask for suggestions on how to optimize a repaint in Compact Framework? GetHashCode() didn't help because it always return a different hash code. Anyway, I have a program which you can drag and resize an object in run time. This object is a transparent object and it has a PNG image which also dynamically resize relative to object client size. Though I noticed, (e.g. I have 4 transparent object and I'm dragging or resizing one) all 4 of them triggers OnPaintBackground even if the 3 are not moving. Another one when am just tapping on the one object .. it sill triggers onPaintBacground(). Anyway, I don't have a problem when this events get triggered. What I like to do is optimization and that means I only have to repaint the object when it's necessary. Can you guys please give a suggestions? here's my pseudo C# code Bitmap _backBuff; onResize() { if(_backBuff != null) _backBuff.Dispose(); _backBuff = new Bitmap(ClientSize.Width, ClientSize.Height); Invalidate(); } onPaintBackground(e) /*have to use onPaintBackground because MSDN said it's faster*/ { using(Graphics g = Graphics.FromImage(_backBuff)) { g.Clear(Color.Black); // draw background ....some interface calling here ....and paint the background // draw alpha PNG .. get hDc .. paint PNG .. release hDc } e.Graphics.DrawImage(_backBuff,0,0); } Thanks in advance.

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• How do I force ode45 to take steps of exactly 0.01 on the T axis?

  - by Gravitas

  I'm using Matlab to solve a differential equation. I want to force ode45 to take constant steps, so it always increments 0.01 on the T axis while solving the equation. How do I do this? ode45 is consistently taking optimized, random steps, and I can't seem to work out how to make it take consistent, small steps of 0.01. Here is the code: options= odeset('Reltol',0.001,'Stats','on'); %figure(1); %clf; init=[xo yo zo]'; tspan=[to tf]; %tspan = t0:0.01:tf; [T,Y]=ode45(name,tspan,init,options);

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• Memcached broken pipe in rails

  - by abronte

  I seem to run into some random broken pipe errors if I try to access memcached a specific way. When I try to access memcached via Rails.cache, the first one or two reads/writes will result in a "MemCacheError (Broken pipe): Broken pipe" and return nil. But if I access memcached through a new object (ActiveSupport::Cache::MemCacheStore.new) I don't get the broken pipe error at all. I've tried upgrading to memcached 1.4.4 (was previously using 1.2.2) and I still got the error. I'm using rails 2.3.5. I would prefer to access memcached through Rails.cache because I takes namespaces into account. Any ideas?

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• Why the following Java code has different outputs each time?

  - by Maxood

  I don't know about threads in Java. I like to know what is happening in this code because each time it runs, it produces a different output: public class TwoThreadsDemo{ public static void main(String[] args) { new SimpleThread("Java Programmer").start(); new SimpleThread("Java Programmer").start(); } } class SimpleThread extends Thread{ public SimpleThread(String str) { super(str); } public void run() { for (int i=0;i<10;i++) { System.out.println(i + " " + getName()); try { sleep((long)(Math.random()*1000)); } catch(InterruptedException e) { } } System.out.println("Done!" + getName()); } }

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• Why is WPFToolkit DataGrid so slow when binding?

  - by Schneider

  I have a very simple test application where I have two objects, each with a small collection of items. when I select an object I display its collection in a WPFToolkit DataGrid. The problem is there is a noticeable delay, such that if you press up/down keys to toggle selection between objects you can see it can't keep up. Why is the performance so bad? <Window x:Class="SlowGridBinding.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:Controls="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit" Title="MainWindow" Height="350" Width="525"> <StackPanel> <ListBox ItemsSource="{Binding Shops}" DisplayMemberPath="Name" IsSynchronizedWithCurrentItem="True"/> <Controls:DataGrid ItemsSource="{Binding Shops/Vegetables}" AutoGenerateColumns="True"/> </StackPanel> The DataContext is populated with some test classes filled with 50 items of random test data.

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• GetWindowPlacement/SetWindowPlacement not working in WinForms for high DPI

  - by RandomEngy

  I've got a legacy WinForms app and I want to save the window position and size across sessions. I've been using GetWindowPlacement and SetWindowPlacement during the FormClosing and Load events. The problem I'm getting is that at higher DPI settings (Such as Medium, size at 125%) the sizes keep inflating. I'll call SetWindowPlacement on it with a certain size, but when GetWindowPlacement is called, those numbers come back 25% bigger, even though the window was the same size all along. The same sort of problem exists when saving the size of a resizable element within the form. Now this works fine if I create a new WinForms project: The size stays stable even when running at the higher DPI. I'm guessing there's some legacy setting in the bowels of the project or some arcane Form setting that's messing it up, but I can't find out where. I've called IsProcessDPIAware on both projects and both are true. Does anyone know what might be causing this?

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• SQL Split function that handles string with delimeter appearing between text qualifiers?

  - by Ron

  There are several SQL split functions, from loop driven, to using xml commands, and even using a numbers table. I haven't found one that supports text qualifiers. Using the example string below, I would like to split on ",", but not when it appears between double or single quotes. Example data: [email protected], "Sally \"Heat\" Jones" <[email protected]>, "Mark Jones" <[email protected]>, "Stone, Ron" <[email protected]> Should return a table: [email protected] "Sally \"Heat\" Jones" <[email protected]> "Mark Jones" <[email protected]> "Stone, Ron" <[email protected]> I know this is a complex query/function, but any suggestions or any guidance would be mucho appreciated.

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• Convert javascript ticks to date in Flot jQuery-plugin issue

  - by Kasper Skov

  I have a dynamic Flot graph with dates on the x-axis and numbers on the y-axis. To get the Flot-plugin to read the date object correctly, I had to convert the dates to ticks (with getTime()). My problem is that I can't revers the ticks back to a normal date in my tooltip hover on the graph. I've tried to revers it with this: dateTimeObject = new Date((jsTicks - 621355968000000000) / 10000); All I get, no matter what jsTicks is, is "Jan 02 0001 hh:mm:ss (almost current time)" What am I doing wrong?

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• Check ReturnUrl is valid before redirecting

  - by Josh

  I'm using ASP.NET Membership and Form Authentication and before redirecting to the returnURL I wanted to validate it. For those unfamiliar with the workflow, basically if you request a page that requires that you are authenticated, you are redirected to a login page. In the URL string you'll see a parameter called returnURL, e.g. http://example.com/login.aspx?ReturnUrl=%2fprotected%2fdefault.aspx Whether you use this in a redirect such as Response.Redirect(returnURL) or indirectly through the FormsAuthentication.RedirectFromLoginPage method, it passes without validating returnURL. FormsAuthentication.RedirectFromLoginPage does have a security check that it is isn't leaving the domain, but that still doesn't stop someone from putting enough random characters to cause an error. I tried using System.IO.File.Exists(Server.MapPath(returnURL)) but given enough illegal characters it cause Server.MapPath to error. Note: URLEncoding doesn't work because we are not cleaning a parameter, but the primary URL. Any other suggestions for validating or cleaning the returnURL value?

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• Are there alternatives to UltraWinGrid (for C#)?

  - by MPelletier

  I've been using the Infragistics UltraWinGrid for a while in a C# project, and while it's very spiffy, it is sometimes a bit heavy to run (and editing it in Visual Studio can be hazardous). I'm looking for a lighter alternative. Looks (always a big plus with Infragistics) are not as important as functionality. Namely, I'm looking for a beefed up DataGridView which: has data binding (duh!) has lock control over editing allows for sub-tables on opening a row can have multiple headers to group columns together (say header 1 is composed of "Group A" and "Group B", and header 2 has various columns under each group) has sorting by column (and can sort numbers properly, even if it does not have a stock method at first) has filtering by column (perhaps the most demanding spec) à la UltraWinGrid/Excel (text field with a way to specify if the filter is equal, not equal, greater, lesser, starts with, ends with, etc). supports check box, text box or data bound list/combo box cells allows cells to be merged (not the control cells of course!) can have events bound to each row (say double click)

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• LGPL and Dual Licensing Ajax Library

  - by Thomas Hansen

  Hi guys, I'm the previous founder of Gaiaware and Gaia Ajax Widgets and when I used to work there we had this rhetoric (which I have confirmed with some very smart FOSS people is correct) that when using a GPL Ajax library you're basically "distributing" the JavaScript which in turn makes the GPL viral clause kick in and forces people to purchase a proprietary license if they're going to build Closed Source stuff... So now I'm the the LGPL world here with Ra-Ajax which is an LGPL licensed library and I've got no intentions of creating a GPL licensed library since I believe strongly in that the LGPL is the "enabler" of the Open Web to prevail. But something interesting have happened which I think might still give me a "business model" here which is the Linking clause of the LGPL which I think goes something like this (pseudo); "If you link to an LGPL licensed thing you get no restrictions on your own derived works"... But so we started creating something we're calling Ajax Starter-Kits which effectively is a "Project Kickstarter" where you can download a finished project/solution which basically enables you to start out with some pre-done boiler plate code for problems such as Ajax DataGrids, Ajax Calendar Applications, Ajax TreeView Applications etc. And the funny thing is that our users would NOT "link" to these, they would effectively BE our users applications... So to wrap up my question. Would this force users of our LGPL licensed Ajax Starter-Kits to LGPL license their own work? Basically if it does we have a business model (and I get very happy) if not I'd just have to hope people would still like to pay us those $29 for our Starter-Kits to support the project... ;) Help rewarded with extreme gratitude...

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• When to use Shift operators << >> in C# ?

  - by Junior Mayhé

  I was studying shift operators in C#, trying to find out when to use them in my code. I found an answer but for Java, you could: a) Make faster integer multiplication and division operations: *4839534 * 4* can be done like this: 4839534 << 2 or 543894 / 2 can be done like this: 543894 1 Shift operations much more faster than multiplication for most of processors. b) Reassembling byte streams to int values c) For accelerating operations with graphics since Red, Green and Blue colors coded by separate bytes. d) Packing small numbers into one single long... For b, c and d I can't imagine here a real sample. Does anyone know if we can accomplish all these items in C#? Is there more practical use for shift operators in C#?

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• pchart pie chart legend and graph not correlating

  - by madphp

  Hi, I have ten values in the dataset, numbers 1 - 10 and corresponding values. Some of the values are coming back as zero, so they are not added to the chart, BUT, the legend is still listing 1 - 10. Because theres values missing in the chart, the colour coding is knocked off. ie Item 1, has a value of zero, its passed over in the chart, the colour in the legend is red, Item 2, has a value of 4, the percentage is calculated, and the chart gives it the colour red which is the colour for item 1 in the legend. Hope that makes sense. How can I print the legend just for the values that are displayed in the chart? --Mark

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• djb2 Hash Function

  - by Jainish

  I am using the djb2 algorithm to generate the hash key for a string which is as follows hash(unsigned char *str) { unsigned long hash = 5381; int c; while (c = *str++) hash = ((hash << 5) + hash) + c; /* hash * 33 + c */ return hash; } Now with every loop there is a multiplication with two big numbers, After some time with the 4th of 5th character of the string there is a overflow as the hash value becomes huge What is the correct way to refactor so that the hash value does not overflow and the hashing also happens correctly

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• Java apache poi setting the cell formula

  - by Ray

  I am try to set a cell formulat that references cells from other workbooks. However, when I open the programmatically generated workbook, the formula cells show up as #REF!. I print out the formulas that were generated in a log. If I cut and paste those into the cells, the numbers from the external workbooks is pulled in. String formula = "'C:\\tmp\\ForecastAggregate\\Total Products\\[ForecastWorksheet.xls]2010 Budget'!C10"; HSSFCell cell = row.createCell(0); //row was created above cell.setCellFormula(formula); Can anybode help?

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• Updating Lists of Lists in Tapestry4 using textfields and a single submit button

  - by Nicolas Scarrci

  In Tapestry 4 I am trying it iterate over a list of lists (technically a list of objects who have a list of strings as a data field). I am currently doing this by using 'nested' for components. (This is pseudo code) <span jwcid="Form"> <span jwcid="@For" source="ognl:Javaclass.TopLevelList" value="ognl:SecondLevelList" index="ognl:index"> <span jwcid="@For" source="ognl:SecondLevelList.List" value="ognl:ListItem" index="ListItemIndex"> <span jwcid="@TextField" value="ognl:ListItem"/> <span jwcid="@Submit" listener="ognl:listeners.onSubmit"/> </span></span></span> The onSubmit listener then accesses the index and ListItem index page properties, as well as the ListItem page property in order to correctly update the list in Javaclass.TopLevelList. This works fine, but it looks terrible, and is cumbersome to the end user. I would prefer to somehow simulate this functionality using only one submit button at the bottom of the page. I have looked into somehow using the overlying form component to obtain a list of the 'form control components' within it, and then (with great care) parsing through tapestry's naming conventions to recover the functionality of the indexes. If anyone knows how to do this, or could explain the form component (how/when it submits, etc.) it would be greatly appreciated.

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• Parse text from a screen grab

  - by Caylem

  Hey guys Not sure the best way to explain this but i'll give it a shot. I'm trying to find a way to parse text/numbers from a screen grab in either C# or Java - whichever provides the easiest way, but preferably java. An example would be as follows. You have a website/document/application with a block of text. You can take a screenshot of the specific area which contains this text. Once the screenshot has been taken you can extract a string from it containing the relevant characters. Any feedback is appreciated. Thanks

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• PHP - Foreach in a foreach + CodeIgniter

  - by Sebhael

  I got an image upload function working, but there's 4 images required in this image. And my current function is simply just overwriting the image despite the number. I'm wondering how I would insert (preferably) a letter into my foreach function. $uploads = array($this->uploads->data()); foreach ( $uploads as $key[] => $value ) { $imagename = $cleaned . '-s' . $value['file_ext']; //outputs clean-name-s.ext } By the time all is said and done, 4 images will require this function. Leaving me with clean-name-sa.ext, clean-name-sb.ext, clean-name-sc.ext, and clean-name-sd.ext (numbers work as well). The form does require that all 4 fields are filled out before submission, so would I just create an array of my desired identifiers and create a foreach loop that outputs 4 different $imagenames? Or is there a simpler, more logical approach to this.

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