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  • 0/1 Knapsack with irrational weights

    - by user356106
    Consider the 0/1 knapsack problem. The standard Dynamic Programming algorithm applies only when the capacity as well as the weights to fill the knapsack with are integers/ rational numbers. What do you do when the capacity/weights are irrational? The issue is that we can't memoize like we do for integer weights because we may need potentially infinite decimal places for irrational weights - leading to an infinitely large number of columns for the Dynamic Programming Table . Is there any standard method for solving this? Any comments on the complexity of this problem? Any heuristics? What about associated recurrences like (for example): f(x)=1, for x< sqrt(2) f(x)=f(x-sqrt(2))+sqrt(3)

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  • Django refresh page if change data by other user

    - by Fran Sobrino
    I have a test django app. In one page the test show the same question to all users. I'd like that when a user answers correctly, send a signal to other active user's browser to refresh to the next question. I have been learning about signals in django I learning work with them but I don't now how send the "refresh signal" to client browser. I think that it can do with a javascript code that check if a certain value (actual question) change and if change reload the page but I don't know this language and the information that I find was confused. Can anybody help me? Many Thanks.

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  • When does it make sense to use a map?

    - by kiwicptn
    I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category and put up an example. Property values (like a bean) age -> 30 sex -> male loc -> calgary Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1

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  • What is a modern C++ approach to structures containing symbolic constants?

    - by Ken
    enum bool { FALSE = 0, TRUE = 1 }; I'm wondering how to translate this in a modern C++ approach and if there is a well suited container for that; i know that the enum are not really that appreciated, but i can't think about a real alternative in the C++ world. What if would like to associate the execution of a particular method with a state? Ok, this is the part where i will be more verbose. I would like to stress the fact that i'm asking about structures symbolic constants and not about TRUE and FALSE, i'm not that "needy". Suppose that i have a structure that can represent several states with their own constants enum semaphore { GREEN = 0, ORANGE = 1, RED = 2 }; this is C code, now my question is about how to do the same in C++ if there is a better way. My question continue when i ask about the possibility to do something like an automatic triggering when a change of state will occur, for example: int main{ ... semaphore = 1; ... } and without any extra statements this has to trigger a method() just because the semaphore is now orange. I hope that is more clear now.

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  • MS SQL Cursor data as result of stored procedure

    - by Dmitry Borovsky
    Hello, I have some stored procedure DECLARE cursor FOR SELECT [FooData] From [FooTable]; OPEN cursor ; FETCH NEXT FROM cursor INTO @CurrFooData; WHILE @@FETCH_STATUS = 0 BEGIN SELECT @CurrFooData AS FooData; INSERT INTO Bar (BarData) VALUES(@CurrFooData); FETCH NEXT FROM cursor INTO @CurrFooData; END; CLOSE OldestFeeds DEALLOCATE OldestFeeds But in result I have a lot of tables, not one. How can I return one table with 'FooData' column and all '@CurrFooData' rows?

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  • Java: Is there a way to efficiently insert or remove many elements from the middle of a LinkedList?

    - by allyourcode
    I was expecting to find this in Java's LinkedList, since the point of linked lists is to be able to efficiently insert (and remove) anywhere (assuming you have some kind of pointer to the location where you want to insert or remove). I'm not finding anything in the API though. Am I overlooking something? The closest thing I can find to this are the add and remove method in ListIterator. This has some limitations though. In particular, other iterators become invalid as soon as the underlying LinkedList is modified via remove, according to the API. This is born out in my tests as well; the following program results in a IllegalStateException: import java.util.*; public class RemoveFromLinkedList { public static void main(String[] args) { LinkedList<Integer> myList= new LinkedList<Integer>(); for (int i = 0; i < 10; ++i) { myList.add(i); } ListIterator<Integer> i1 = myList.listIterator(); ListIterator<Integer> i2 = myList.listIterator(); for (int i = 0; i < 3; ++i) { i1.next(); i2.next(); } System.out.println("i1.next() should be 3: " + i1.next()); i1.remove(); i1.remove(); // Exception! System.out.println("i2.next() should be 5: " + i2.next()); } } Ideally, what I'm expecting is something like this: // In my imagination only. This is the way Java actually works, afaict. // Construct two insertion/deletion points in LinkedList myLinkedList. myIterator = myLinkedList.iterator(); for (...) { myIterator.next(); } start = myIterator.clone(); for (...) { myIterator.next(); } // Later... after = myLinkedList.spliceAfter(myIterator, someOtherLinkedList); // start, myIterator, and after are still all valid; thus, I can do this: // Removes everything I just spliced in, as well as some other stuff before that. myLinkedList.remove(start, after); // Now, myIterator is invalid, but not start, nor after. C++ has something like this for its list class (template). Only iterators pointing to moved elements become invalidated, not ALL iterators.

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  • mysql data being inserted twice via php

    - by Jascha
    I can't for the life of me figure out why this function is causing multiple entries into my database table... When I run the function I end up with two records stacked on top of each one second apart here is the function: function generate_signup_token(){ $connection = new DB_Connect(); // <--- my database connection class $ip = mysql_real_escape_string($_SERVER['REMOTE_ADDR']); $sign_up_token = uniqid(mt_rand(), true); $_SESSION['signup_token'] = $sign_up_token; $sign_up_token = mysql_real_escape_string($sign_up_token); $query = "INSERT INTO `token_manager` (`ip_address`, `signup_token`) VALUES ('$ip', '$sign_up_token')"; mysql_query($query); } generate_signup_token();

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  • If attacker has original data, and encrypted data, can they determine the passphrase?

    - by Brad Cupit
    If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require this extra table. I'm leaning towards the the one-way hash + extra table solution, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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  • get data from a querystring

    - by regwe
    i have this querystring that shall open up my page. http://www.a1-one.com/[email protected]&stuid=123456 Now when this page loads, on page_load, I want to pick up email and stuid in two different variables. So I can use them to insert into my database (sql server) how can this be done in vb.net

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  • php code is not fetching data from mysql database using wamp server

    - by john
    I want to display a table from database in phpMyAdmin by putting the following conditions that in every different options in drop down menu it displays different table from database by pressing the button of search. But it is not doing so. <p class="h2">Quick Search</p> <div class="sb2_opts"> <p></p> <form method="post" action="" > <p>Enter your source and destination.</p> <p>From:</p> <select name="from"> <option value="Islamabad">Islamabad</option> <option value="Lahore">Lahore</option> <option value="murree">Murree</option> <option value="Muzaffarabad">Muzaffarabad</option> </select> <p>To:</p> <select name="To"> <option value="Islamabad">Islamabad</option> <option value="Lahore">Lahore</option> <option value="murree">Murree</option> <option value="Muzaffarabad">Muzaffarabad</option> </select> <input type="submit" value="search" /> </form> </form> </table> <?php $con=mysqli_connect("localhost","root","","test"); if (mysqli_connect_errno()) { echo "Failed to connect to MySQL: " . mysqli_connect_error(); } if(isset($_POST['from']) and isset($_POST['To'])) { $from = $_POST['from'] ; $to = $_POST['To'] ; $table = array($from, $to); switch ($table) { case array ("Islamabad", "Lahore") : $result = mysqli_query($con,"SELECT * FROM flights"); echo "</flights>"; //table name is flights break; case array ("Islamabad", "Murree") : $result = mysqli_query($con,"SELECT * FROM isb to murree"); echo "</isb to murree>"; //table name isb to murree ; break; case array ("Islamabad", "Muzaffarabad") : $result = mysqli_query($con,"SELECT * FROM isb to muzz"); echo "</isb to muzz>"; break; //..... //...... default: echo "Your choice is nor valid !!"; } } mysqli_close($con); ?>

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  • Store address dynamic array in c

    - by user280642
    I'm trying to save the address of a dynamic array index. struct sstor *dlist; struct node *q; q->item = &(dlist->item[(dlist->sz)-1]); // Problem? This is my node struct node { char **item; struct node *next; struct node *prev; }; This is my array struct sstor { int sz; int maxsz; char item[][1024]; }; I'm still new to pointers. The line below gives the error: assignment from incompatible pointer type q->item = &(dlist->item[(dlist->sz)-1]);

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  • Reading data from text file in C

    - by themake
    I have a text file which contains words separated by space. I want to take each word from the file and store it. So i have opened the file but am unsure how to assign the word to a char. FILE *fp; fp = fopen("file.txt", "r"); //then i want char one = the first word in the file char two = the second word in the file

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  • Entity framework using Data Repository pattern

    - by JamesStuddart
    Hi all, I have been implementing a new project which I have decided to use the repository pattern and Entity Framework. I have sucessfuly implemented basic CRUD methods and I have no moved onto my DeepLoads. From all the examples and documentation I can find to do this I need to call something like this: public Foo DeepLoadFoo() { return (from foobah in Context.Items.Include("bah").Include("foo").Include("foofoo") select foo).Single(); } This doesnt work for me, maybe I am trying to be too lazy but what I would like to achieve would be something along the lines of this: public Foo DeepLoadFoo(Foo entity, Type[] childTypes) { return (from foobah in Context.Items.Include(childTypes).Single(); } Is anything like this possible, or am I stuck with include.include.include.include? Thanks

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  • add extra data to response object to render in template

    - by mp0int
    I ned to write a code sniplet that enables to disable connection to some parts of a site. Admin and the mainpage will be displayable, but user section (which uses ajax) will be displayed, but can not be used (vith a transparent div set over the page). Also there is a few pages which will be disabled. my logic is that, i write a middleware, def process_request(self, request): if ayar.tonline_kapali: url_parcalari = request.path.split('/') if url_parcalari[0] not in settings.BAGIMSIZ_URLLER: if not request.is_ajax(): return render_to_response('bakim_modu.html') else: return None that code let me to display a "site closed" message for the urls not in BAGIMSIZ_URLLER (which contains urls that will be accessible) But i do not figure out how can i solve the problem about ajax pages... i need to set a header or something to the response and need to check it in the template.

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  • Best way to model Customer <--> Address

    - by Jen
    Every Customer has a physical address and an optional mailing address. What is your preferred way to model this? Option 1. Customer has foreign key to Address Customer (id, phys_address_id, mail_address_id) Address (id, street, city, etc.) Option 2. Customer has one-to-many relationship to Address, which contains a field to describe the address type Customer (id) Address (id, customer_id, address_type, street, city, etc.) Option 3. Address information is de-normalized and stored in Customer Customer (id, phys_street, phys_city, etc. mail_street, mail_city, etc.) One of my overriding goals is to simplify the object-relational mappings, so I'm leaning towards the first approach. What are your thoughts?

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  • MATLAB: draw centroids

    - by Myx
    Hello - my main question is given a feature centroid, how can I draw it in MATLAB? In more detail, I have an NxNx3 image (an rgb image) of which I take 4x4 blocks and compute a 6-dimensional feature vector for each block. I store these feature vectors in an Mx6 matrix on which I run kmeans function and obtain the centroids in a kx6 matrix, where k is the number of clusters and 6 is the number of features for each block. How can I draw these center clusters in my image in order to visualize if the algorithm is performing the way I wish it to perform? Or if anyone has any other way/suggestions on how I can visualize the centroids on my image, I'd greatly appreciate it. Thank you.

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  • Can not issue data manipulation statements with executeQuery in java

    - by user225269
    I'm trying to insert records in mysql database using java, What do I place in this code so that I could insert records: String id; String name; String school; String gender; String lang; Scanner inputs = new Scanner(System.in); System.out.println("Input id:"); id=inputs.next(); System.out.println("Input name:"); name=inputs.next(); System.out.println("Input school:"); school= inputs.next(); System.out.println("Input gender:"); gender= inputs.next(); System.out.println("Input lang:"); lang=inputs.next(); Class.forName("com.mysql.jdbc.Driver"); Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/employee_record", "root", "MyPassword"); PreparedStatement statement = con.prepareStatement("insert into employee values('id', 'name', 'school', 'gender', 'lang');"); statement.executeUpdate();

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  • Django form and User data

    - by Dean
    I have a model that looks like this: class Client(models.Model): name = models.CharField(max_length=100, primary_key=True) user = models.ForeignKey(User) class Contract(models.Model): title = models.CharField(max_length=100, primary_key=True) start_date = models.DateField() end_date = models.DateField() description = models.TextField() client = models.ForeignKey(Client) user = models.ForeignKey(User) How can i configure a django form so that only clients associated with that user show in the field in the form? My initial thought was this in my forms.py: client = forms.ModelChoiceField(queryset=Client.objects.filter(user__username = User.username)) But it didn't work. So how else would I go about it?

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  • PHP : How to get specific data from array

    - by Giffary
    Hello! I try to use amazon API using PHP. If I use print_r($parsed_xml->Items->Item->ItemAttributes) it show me some result like SimpleXMLElement Object ( [Binding] = Electronics [Brand] = Canon [DisplaySize] = 2.5 [EAN] = 0013803113662 [Feature] = Array ( [0] = High-powered 20x wide-angle optical zoom with Optical Image Stabilizer [1] = Capture 720p HD movies with stereo sound; HDMI output connector for easy playback on your HDTV [2] = 2.5-inch Vari-Angle System LCD; improved Smart AUTO intelligently selects from 22 predefined shooting situations [3] = DIGIC 4 Image Processor; 12.1-megapixel resolution for poster-size, photo-quality prints [4] = Powered by AA batteries (included); capture images to SD/SDHC memory cards (not included) ) [FloppyDiskDriveDescription] = None [FormFactor] = Rotating [HasRedEyeReduction] = 1 [IsAutographed] = 0 [IsMemorabilia] = 0 [ItemDimensions] = SimpleXMLElement Object ( [Height] = 340 [Length] = 490 [Weight] = 124 [Width] = 350 ) [Label] = Canon [LensType] = Zoom lens [ListPrice] = SimpleXMLElement Object ( [Amount] = 60103 [CurrencyCode] = USD [FormattedPrice] = $601.03 ) [Manufacturer] = Canon [MaximumFocalLength] = 100 [MaximumResolution] = 12.1 [MinimumFocalLength] = 5 [Model] = SX20IS [MPN] = SX20IS [OpticalSensorResolution] = 12.1 [OpticalZoom] = 20 [PackageDimensions] = SimpleXMLElement Object ( [Height] = 460 [Length] = 900 [Weight] = 242 [Width] = 630 ) [PackageQuantity] = 1 [ProductGroup] = Photography [ProductTypeName] = CAMERA_DIGITAL [ProductTypeSubcategory] = point-and-shoot [Publisher] = Canon [Studio] = Canon [Title] = Canon PowerShot SX20IS 12.1MP Digital Camera with 20x Wide Angle Optical Image Stabilized Zoom and 2.5-inch Articulating LCD [UPC] = 013803113662 ) my goal is to get only Feature infomation and I try to use $feature = $parsed_xml->Items->Item->ItemAttributes->Feature it does'not work for me because it just show me the first feature only. How do i get all feature information? please help

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  • Wrong data retrieved from database

    - by holyredbeard
    So, I want to retrieve the order of the elements of a list. The order is set before by the user, and are stored in the table below. Because I also want to retrieve name and description of the list elements I need to combine two tables (see below). However, what is actually retrieved is an array containing 16 elements (should be four because it only exists four elements as for now). The array is too long to post here, but I put it in a phpFiddle to be found here if you're interested. Well, I have really tried to find what's wrong (probably something easy as always), but with no luck. Thanks a lot for your time and help! listModel.php: public function GetOrderedElements($userId, $listId) { // $userId = 46 // $listId = 1 $query = "SELECT le.listElemId, le.listElemName, le.listElemDesc, lo.listElemOrderPlace FROM listElement AS le INNER JOIN listElemOrder AS lo ON le.listId = lo.listId WHERE lo.userId = ? AND lo.listId = ? ORDER BY listElemId"; $stmt = $this->m_db->Prepare($query); $stmt->bind_param("ii", $userId, $listId); $listElements = $this->m_db->GetOrderedElements($stmt); return $listElements; } database.php: public function GetOrderedElements(\mysqli_stmt $stmt) { if ($stmt === FALSE) { throw new \Exception($this->mysqli->error); } if ($stmt->execute() == FALSE) { throw new \Exception($this->mysqli->error); } if ($stmt->bind_result($listElemId, $listElemName, $listElemDesc, $listElemOrderPlace) == FALSE) { throw new \Exception($this->mysqli->error); } $listElements = array(); while ($stmt->fetch()) { $listElements[] = array('listElemId' => $listElemId, 'listElemName' => $listElemName, 'listElemDesc' => $listElemDesc, 'listElemOrderPlace' => $listElemOrderPlace); } var_dump($listElements); $stmt->Close(); return $listElements; } from the database: listElemOrder: listElemOrderId | listId | listElemId | userId | listElemOrderPlace 1 1 1 46 1 2 1 2 46 4 3 1 3 46 2 4 1 4 46 3 listElement: listElemId | listElemName | listId | listElemDesc | listElemOrderPlace 1 Elem A 1 Derp NULL 2 Elem B 1 Herp NULL 3 Elem C 1 Lorum NULL 4 Elem D 1 Ipsum NULL Note: 'listElemOrderPlace' in the table listElement is the final order of the elements (all users average), not to be mixed with the one with the same name in the other table, that's only a specific user's order of the list elements (which is the interesting one in this case).

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  • Android , Read in binary data and write it to file

    - by Shpongle
    Hi all , Im trying to read in image file from a server , with the code below . It keeps going into the exception. I know the correct number of bytes are being sent as I print them out when received. Im sending the image file from python like so #open the image file and read it into an object imgfile = open (marked_image, 'rb') obj = imgfile.read() #get the no of bytes in the image and convert it to a string bytes = str(len(obj)) #send the number of bytes self.conn.send( bytes + '\n') if self.conn.sendall(obj) == None: imgfile.flush() imgfile.close() print 'Image Sent' else: print 'Error' Here is the android part , this is where I'm having the problem. Any suggestions on the best way to go about receiving the image and writing it to a file ? //read the number of bytes in the image String noOfBytes = in.readLine(); Toast.makeText(this, noOfBytes, 5).show(); byte bytes [] = new byte [Integer.parseInt(noOfBytes)]; //create a file to store the retrieved image File photo = new File(Environment.getExternalStorageDirectory(), "PostKey.jpg"); DataInputStream dis = new DataInputStream(link.getInputStream()); try{ os =new FileOutputStream(photo); byte buf[]=new byte[1024]; int len; while((len=dis.read(buf))>0) os.write(buf,0,len); Toast.makeText(this, "File recieved", 5).show(); os.close(); dis.close(); }catch(IOException e){ Toast.makeText(this, "An IO Error Occured", 5).show(); } EDIT: I still cant seem to get it working. I have been at it since and the result of all my efforts have either resulted in a file that is not the full size or else the app crashing. I know the file is not corrupt before sending server side. As far as I can tell its definitely sending too as the send all method in python sends all or throws an exception in the event of an error and so far it has never thrown an exception. So the client side is messed up . I have to send the file from the server so I cant use the suggestion suggested by Brian .

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  • How do I get 2-way data binding to work for nested asp.net Repeater controls

    - by jimblanchard
    I have the following (trimmed) markup: <asp:Repeater ID="CostCategoryRepeater" runat="server"> <ItemTemplate> <div class="costCategory"> <asp:Repeater ID="CostRepeater" runat="server" DataSource='<%# Eval("Costs")%>'> <ItemTemplate> <tr class="oddCostRows"> <td class="costItemTextRight"><span><%# Eval("Variance", "{0:c0}")%></span></td> <td class="costItemTextRight"><input id="SupplementAmount" class="costEntryRight" type="text" value='<%# Bind("SupplementAmount")%>' runat="server" /></td> </tr> </ItemTemplate> </asp:Repeater> </div> </ItemTemplate> </asp:Repeater> The outer repeater's DataSource is set in the code-beside. I've snipped them, but there are Eval statements that wire up to the properties in the outer Repeater. Anyway, one of the fields in the inner Repeater needs to be a Bind instead of an Eval, as I want to get the values that the user types in. The SupplementAmount input element correctly receives it's value when the page loads, but on the other side, when I inspect the contents of the Costs List when the form posts back, the changes the user made aren't present. Thanks.

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  • How to store MySQL query results in another Table?

    - by Taz
    How to store results from following query into another table. Considering there is an appropriate table already created. SELECT labels.label,shortabstracts.ShortAbstract,images.LinkToImage,types.Type FROM ner.images,ner.labels,ner.shortabstracts,ner.types WHERE labels.Resource=images.Resource AND labels.Resource=shortabstracts.Resource AND labels.Resource=types.Resource;

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