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  • How do I create a point system in a Rails/Twitter app that assigns points to users and non-authentic

    - by codyvbrown
    I'm building a question and answer application on top of twitter and I'm hitting some snags because I'm inevitably dealing with two classes of users: authenticated and non-authenticated. The site enable users to give points to other users, who may or may not be authenticated, and I want to create a site-wide point system where the application stores and displays this information on their profile. I want to save this point data to the user because that would be faster and more efficient but non-authenticated users aren't in our system, we only have the twitter handle. So instead we display the points in our system like this: @points = point.all( :select => "tag, count(*) AS count", # Return tag and count :group => 'tag', # Group by the tag :order => "2 desc", :conditions => {:twitter_handle => params[:username]}) Is there a better way to do this? Is there a better way to associate data with non-authenticated users?

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  • RegEx to Reject Unescaped Character

    - by JDV72
    I want to restrict usage of unescaped ampersands in a particular input field. I'm having trouble getting a RegEx to kill usage of "&" unless followed by "amp;"...or perhaps just restrict usage of "& " (note the space). I tried to adapt the answer in this thread, but to no avail. Thanks. (FWIW, here's a RegEx I made to ensure that a filename field didn't contain restrited chars. and ended in .mp3. It works fine, but does it look efficient?)

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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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  • Finding mySQL duplicates, then merging data

    - by Michael Pasqualone
    I have a mySQL database with a tad under 2 million rows. The database is non-interactive, so efficiency isn't key. The (simplified) structure I have is: `id` int(11) NOT NULL auto_increment `category` varchar(64) NOT NULL `productListing` varchar(256) NOT NULL Now the problem I would like to solve is, I want to find duplicates on productListing field, merge the data on the category field into a single result - deleting the duplicates. So given the following data: +----+-----------+---------------------------+ | id | category | productListing | +----+-----------+---------------------------+ | 1 | Category1 | productGroup1 | | 2 | Category2 | productGroup1 | | 3 | Category3 | anotherGroup9 | +----+-----------+---------------------------+ What I want to end up is with: +----+----------------------+---------------------------+ | id | category | productListing | +----+----------------------+---------------------------+ | 1 | Category1,Category2 | productGroup1 | | 3 | Category3 | anotherGroup9 | +----+----------------------+---------------------------+ What's the most efficient way to do this either in pure mySQL query or php?

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  • Joining two tables (through a link), one which may yield multiple rows, together into one result.

    - by Eikern
    Lets say I've got a table listing car brands or models: Cars: Id | Brand ----------- 1 | BMW 2 | Audi 3 | Volvo And I've also got another table which links features. Link: Id | carid | featureid ----------------------- 1 | 1 | 1 2 | 1 | 2 3 | 2 | 2 4 | 3 | 1 5 | 3 | 2 6 | 3 | 3 And I've got the table listing the features. Features: Id | Feature ----------- 1 | A/C 2 | 4WD 3 | Heated seats I want to list these results on my front page like this: BMW A/C 4WD Audi 4WD Volvo A/C 4WD Heated seats What's the best/most efficient way of doing this (using PHP and MySQL)?

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  • How to find the largest square in the number (Java)

    - by Ypsilon IV
    Hello everyone, I want to find the largest square in the number, but I am stuck at some point. I would really appreciate some suggestions. This is what I've done so far: I take the number on the input, factorize into prime numbers, and put the sequence of prime numbers to ArrayList. Numbers are sorted, in a sense, thus the numbers in the sequence are increasing. For example, 996 is 2 2 3 83 1000 is 2 2 2 5 5 5 100000 is 2 2 2 2 2 5 5 5 5 5 My idea now is to count number of occurrences of each elements in the sequence, so if the number of occurrences is divisible by two, then this is the square. In this way, I can get another sequence, where the right most element divisible by two is the largest square. What is the most efficient way to count occurrences in the ArrayList? Or is there any better way to find the largest square? Many thanks in advance!

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  • Effective way of String splitting

    - by openidsujoy
    I have a completed string like this N:Pay in Cash++RGI:40++R:200++T:Purchase++IP:N++IS:N++PD:PC++UCP:598.80++UPP:0.00++TCP:598.80++TPP:0.00++QE:1++QS:1++CPC:USD++PPC:Points++D:Y++E:Y++IFE:Y++AD:Y++IR:++MV:++CP:~ ~N:ERedemption++RGI:42++R:200++T:Purchase++IP:N++IS:N++PD:PC++UCP:598.80++UPP:0.00++TCP:598.80++TPP:0.00++QE:1++QS:1++CPC:USD++PPC:Points++D:Y++E:Y++IFE:Y++AD:Y++IR:++MV:++CP: this string is like this It's list of PO's(Payment Options) which are separated by ~~ this list may contains one or more PO contains only Key-Value Pairs which separated by : spaces are denoted by ++ I need to extract the values for Key "RGI" and "N". I can do it via for loop , I want a efficient way to do this. any help on this.

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  • How to hash and check for equality of objects with circular references

    - by mfya
    I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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  • What is the best way to find the digit at n position in a decimal number?

    - by Elijah
    Background I'm working on a symmetric rounding class and I find that I'm stuck with regards to how to best find the number at position x that I will be rounding. I'm sure there is an efficient mathematical way to find the single digit and return it without having to resort to string parsing. Problem Suppose, I have the following (C#) psuedo-code: var position = 3; var value = 102.43587m; // I want this no ? (that is 5) protected static int FindNDigit(decimal value, int position) { // This snippet is what I am searching for } Also, it is worth noting that if my value is a whole number, I will need to return a zero for the result of FindNDigit. Does anyone have any hints on how I should approach this problem? Is this something that is blaringly obvious that I'm missing?

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  • Injecting a dependancy into a base class

    - by Jamie Dixon
    Hey everyone, I'm on a roll today with questions. I'm starting out with Dependency Injection and am having some trouble injecting a dependency into a base class. I have a BaseController controller which my other controllers inherit from. Inside of this base controller I do a number of checks such as determining if the user has the right privileges to view the current page, checking for the existence of some session variables etc. I have a dependency inside of this base controller that I'd like to inject using Ninject however when I set this up as I would for my other dependencies I'm told by the compiler that: Error 1 'MyProject.Controllers.BaseController' does not contain a constructor that takes 0 argument This makes sense but I'm just not sure how to inject this dependency. Should I be using this pattern of using a base controller at all or should I be doing this in a more efficient/correct way?

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  • Detecting similar words among n text documents

    - by javanes
    Hi; I have n documents and want to find common words that are included in these documents. For example I want to say (n-3) documents include the word "web". Certainly I can do this by basic data structures but there maybe efficient algorithm or a way to handle same words with different suffix. Is there any algorithm for such purposes? I am unfamiliar with datamining world. In general manner is there a term used for efforts of finding similarities between different documents? If there is then I will make my research easily. Thanks.

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  • Best place to store large amounts of session data

    - by audiopleb
    I'm building an application that needs to store and re-use large amounts of data per session. So for example, the user selects a large list of list items (say 2000 or significantly more) which have a numeric value as their key then they save that selection and go off to another page, do something else and then come back to the original page and need to load their selections into that page. What is the quickest and most efficient way of storing and reusing that data? In a text file saved with the session id? In a temp db table? In the session data itself (db sessions so size isn't a limit) using a serialised string or using gzcompress or gzencode? Any advice or insight would be great! Thank you!!!!

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  • What's a good algorithm for searching arrays N and M, in order to find elements in N that also exist

    - by GenTiradentes
    I have two arrays, N and M. they are both arbitrarily sized, though N is usually smaller than M. I want to find out what elements in N also exist in M, in the fastest way possible. To give you an example of one possible instance of the program, N is an array 12 units in size, and M is an array 1,000 units in size. I want to find which elements in N also exist in M. (There may not be any matches.) The more parallel the solution, the better. I used to use a hash map for this, but it's not quite as efficient as I'd like it to be. Typing this out, I just thought of running a binary search of M on sizeof(N) independent threads. (Using CUDA) I'll see how this works, though other suggestions are welcome.

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  • Help with MySQL database structure - user notification system

    - by Simon
    Hi, I'd like to send global notifications to my users (1000+ users) and allow them to close the notification box once they have read the message. Basically I may send one notification per week globally ie/ each user get the same message and they are not personal in nature. What is the best way to achieve this? Create 2 tables: **tb_messages** message_id massage_title message_content **tb_read_messages** user_id message_id is-read That way i can just show each user the current notifications that are not read? select * from tb_read_messages WHERE user_id = $user_id AND is-read = no OR is there a more efficient way? Thanks!!!

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  • Obtain patterns in one file from another using ack or awk or better way than grep?

    - by Rock
    Is there a way to obtain patterns in one file (a list of patterns) from another file using ack as the -f option in grep? I see there is an -f option in ack but it's different with the -f in grep. Perhaps an example will give you a better idea. Suppose I have file1: file1: a c e And file2: file2: a 1 b 2 c 3 d 4 e 5 And I want to obtain all the patterns in file1 from file2 to give: a 1 c 3 e 5 Can ack do this? Otherwise, is there a better way to handle the job (such like awk or using hash) because I have millions of records in both files and really need an efficient way to complete? Thanks!

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  • Differentiate A Section/Portion of 3D object From Other Parts

    - by Ramshad
    I am trying to write a WPF windows application that dynamically creates a 3 D object for an existing 3D Image. The senerio is as follows. Mark the points randomly on the existing 3D Image. Create a 3D object based on the points already marked. Check the below Sample Screenshots. Screenshot 1 and Screenshot 2 I am successfully able to load the 3D file to the WPF form. And was able to perform the rotation using TrackballDecorator 3D Tools library. I have just read this related post. however i didn't get it exactly :) So,can you suggest some efficient methods to achieve it.

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  • What's the best way to implement one-dimensional collision detection?

    - by cyclotis04
    I'm writing a piece of simulation software, and need an efficient way to test for collisions along a line. The simulation is of a train crossing several switches on a track. When a wheel comes within N inches of the switch, the switch turns on, then turns off when the wheel leaves. Since all wheels are the same size, and all switches are the same size, I can represent them as a single coordinate X along the track. Switch distances and wheel distances don't change in relation to each other, once set. This is a fairly trivial problem when done through brute force by placing the X coordinates in lists, and traversing them, but I need a way to do so efficiently, because it needs to be extremely accurate, even when the train is moving at high speeds. There's a ton of tutorials on 2D collision detection, but I'm not sure the best way to go about this unique 1D scenario.

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  • apache commons http client efficiency

    - by wo_shi_ni_ba_ba
    I use apache commons http client to send data via post every second, is there a way to make the following code more efficient? I know http is stateless, but is there anything I can do to improve since the base url is always the same in this case(only the parameter value change. private void sendData(String s){ try { HttpClient client = getHttpClient(); HttpPost method = new HttpPost("http://192.168.1.100:8080/myapp"); System.err.println("send to server "+s); List formparams = new ArrayList(); formparams.add(new BasicNameValuePair("packet", s)); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8"); method.setEntity(entity); HttpResponse resp=client.execute(method); String res = EntityUtils.toString(resp.getEntity()); System.out.println(res); } catch (Exception e) { e.printStackTrace(); } } private HttpClient getHttpClient() { if(httpClient==null){ httpClient = new DefaultHttpClient(); } return httpClient; }

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  • Algorithm Question.. Linked List..

    - by AGeek
    Hi, Scenario is as follows:- I want to reverse the direction of the singly linked list, In other words, after the reversal all pointers should now point backwards.. Well the algorithm should take linear time. The solution that i have thought of using another datastructure A Stack.. With the help of which the singly linked list would be easily reversed, with all pointers pointing backwards.. But i am in doubt, that whether the following implementation yeild linear time complexity.. Please comment on this.. And if any other efficient algorithm is in place, then please discuss.. Thanks.

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  • CSV parser in C++

    - by User1
    All I need is a good CSV file parser for C++. At this point it can really just be a comma-delimited parser (ie don't worry about escaping new lines and commas). The main need is a line-by-line parser that will return a vector for the next line each time the method is called. I found this article which looks quite promising: http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/list_parser.cpp I've never used Boost's Spirit, but am willing to try it. Is it overkill/bloated or is it fast and efficient? Does anyone have faster algorithms using STL or anything else? Thanks!

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  • Efficiently using position to control actions

    - by John Ashmore
    I want to use position (returned from a gridview for e.g.) or a similar numeric integer to do various things, e.g. create a sprite, or in any command that wants something other than a number, e.g. I want to use something like: sprites.add(createSprite(R.drawable.image(position)); , where createSprite creates a sprite using the image supplied, instead of: if (position == 1) {sprites.add(createSprite(R.drawable.image1);} if (position == 2) {sprites.add(createSprite(R.drawable.image2);} ...etc There is an easy solution for strings: Most efficient method to use position to open a .java but what about for situations like this one?

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  • Force download menu for remote files

    - by o-logn
    Hey, I would like users to upload links on my site. When another user clicks on the link (e.g. PDF file), then I would like the download popup to show instead of actually displaying the PDF in browser. I know I can use Response.AddHeader/Response.WriteFile to achieve this, but the WriteFile method required a virtual path. However, the links uploaded by the user will be pointing to external servers. Can I still force the download popup to show and, if so, what would be the most efficient way of doing it? Thanks for any advice

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  • Most efficent way to limit rows returns from union query- TSQL

    - by stephen776
    Hey guys...I have a simple stored proc with two queries joined with a union select name as 'result' from product where... union select productNum as 'result' from product where... I want to limit this to the TOP 10 results... if i put TOP 10 in each seperate query I get 20 results total. What is the most efficient way to limit total results to 10? I dont want to do TOP 5 in each because I may end up in a situation where I have something like 7 "names" and 3 "productsNumbers"

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  • Manage dirty rect efficiently

    - by Tianzhou Chen
    Hi all, I am implementing a view system and I want to keep track of all the dirty rects. It seems my dirty rect management is a bottleneck for the whole system. On one hand, invalidating the bounding box of the dirty region seems to be an easy approach. But in the situation like this: Say I have a client area of 100x100; I have a dirty rect with (0, 0, 1, 1) and another dirty rect with (99, 99, 1, 1). Invalidating the bounding box which turns out to be 100x100 is not efficient at all. So I want to ask if someone can give any hint or give me a link of the related literatures. Thanks in advance!

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  • Enumerating combinations in a distributed manner

    - by Reyzooti
    I have a problem where I must analyse 500C5 combinations (255244687600) of something. Distributing it over a 10 node cluster where each cluster processes roughly 10^6 combinations per second means the job will be complete in about 7hours. The problem I have is distributing the 255244687600 combinations over the 10 nodes. I'd like to present each node with 25524468760, however the algorithms I'm using can only produce the combinations sequentially, I'd like to be able to pass the set of elements and a range of combination indicies eg: [0-10^7) or [10^7,2.0 10^7) etc and have the nodes themselves figure out the combinations. The algorithms I'm using at the moment are from the following: http://home.roadrunner.com/~hinnant/combinations.html A logical question I've considered using a master node, that enumerates each of the combinations and sends work to each of the nodes, however the overhead incurred in iterating the combinations from a single node and communicating back and forth work is enormous, and will subsequently lead to the master node becoming the bottleneck. Are there any good combination iterating algorithms geared up for efficient/optimal distributed enumeration?

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