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  • Big O complexity of simple for not always linear?

    - by i30817
    I'm sure most of you know that a nested loop has O(n^2) complexity if the function input size is n for(int i = 0; i < n; i++){ for(int j = 0; j < n; j++){ ... } } I think that this is similar, by a analogous argument, but i'm not sure can anyone confirm? for(int i = 0, max = n*n; i < max; i++{ ... } If so i guess that there is some kinds of code whose big O mapping is not immediately obvious besides recursion and subroutines.

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  • UIView Animation iPhone (obtaining information on the frame dynamically)

    - by Urizen
    I have a UIView called goalBar which is being animated by increasing the size of the frame according to a float value called destination: CGRect goalBarRect = CGRectMake(0, 0, destination, 29); [UIView beginAnimations:@"goal" context:nil]; [UIView setAnimationCurve:UIViewAnimationCurveEaseIn]; [UIView setAnimationDuration:2.0f]; goalBar.frame = goalBarRect; [UIView commitAnimations]; The animation works perfectly and the rectangular view increases its width over the course of the animation (from 0 to the value for destination). However, I wish to be able to extract the values for the frame of the UIView being animated (i.e. goalBar) as the animation takes place. By that I mean that I wish to place the value of the width for the animated frame in a separate UILabel so that the user sees a counter that provides the width of the UIView as it's being animated. Any help on how to do the above would be gratefully received.

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  • Calculate shortest path through a grocery store

    - by Bart
    Hi, I'm trying to find a way to find the shortest path through a grocery store, visiting a list of locations (shopping list). The path should start at a specified startposition and can end at multiple endpositions (there are multiple checkout counters). Also, I have some predefined constraints on the path, such as "item x on the shopping list needs to be the last, second last, or third last item on the path". There is a function that will return true or false for a given path. Finally, this needs to be calculated with limited cpu power (on a smartphone) and within a second or so. If this isn't possible, then an approximation to the optimal path is also ok. Is this possible? So far I think I need to start by calculating the distance between every item on the list using something like A* or Dijkstra's. After that, should I treat it like the travelling salesman problem? Because in my problem there is a specified startnode, specified endnodes, and some constraints, which are not in the travelling salesman problem. Any help would be appreciated :)

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  • Can you find a pattern to sync files knowing only dates and filenames?

    - by Robert MacLean
    Imagine if you will a operating system that had the following methods for files Create File: Creates (writes) a new file to disk. Calling this if a file exists causes a fault. Update File: Updates an existing file. Call this if a file doesn't exist causes a fault. Read File: Reads data from a file. Enumerate files: Gets all files in a folder. Files themselves in this operating system only have the following meta data: Created Time: The original date and time the file was created, by the Create File method. Modified Time: The date and time the file was last modified by the Update File method. If the file has never been modified, this will equal the Create Time. You have been given the task of writing an application which will sync the files between two directories (lets call them bill and ted) on a machine. However it is not that simple, the client has required that The application never faults (see methods above). That while the application is running the users can add and update files and those will be sync'd next time the application runs. Files can be added to either the ted or bill directories. File names cannot be altered. The application will perform one sync per time it is run. The application must be almost entirely in memory, in other words you cannot create a log of filenames and write that to disk and then check that the next time. The exception to point 6 is that you can store date and times between runs. Each date/time is associated with a key labeled A through J (so you have 10 to use) so you can compare keys between runs. There is no way to catch exceptions in the application. Answer will be accepted based on the following conditions: First answer to meet all requirements will be accepted. If there is no way to meet all requirements, the answer which ensures the smallest amount of missed changes per sync will be accepted. A bounty will be created (100 points) as soon as possible for the prize. The winner will be selected one day before the bounty ends. Please ask questions in the comments and I will gladly update and refine the question on those.

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  • Finding the Reachability Count for all vertices of a DAG

    - by ChrisH
    I am trying to find a fast algorithm with modest space requirements to solve the following problem. For each vertex of a DAG find the sum of its in-degree and out-degree in the DAG's transitive closure. Given this DAG: I expect the following result: Vertex # Reacability Count Reachable Vertices in closure 7 5 (11, 8, 2, 9, 10) 5 4 (11, 2, 9, 10) 3 3 (8, 9, 10) 11 5 (7, 5, 2, 9, 10) 8 3 (7, 3, 9) 2 3 (7, 5, 11) 9 5 (7, 5, 11, 8, 3) 10 4 (7, 5, 11, 3) It seems to me that this should be possible without actually constructing the transitive closure. I haven't been able to find anything on the net that exactly describes this problem. I've got some ideas about how to do this, but I wanted to see what the SO crowd could come up with.

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  • How do I show information to users belonging to different groups (web) in modx

    - by Gaurav Sharma
    Hello Everyone, I have created a website using modx evolution v1.0.2. The website that I have developed has 12 different types of users (categorized in groups). Each user will be shown a different price depending on the group to which he belongs. Till now I have been able to fetch the group name of current logged in user (created a snippet for that), but how can I achieve the above mentioned functionality so that each user should be able to see only the price that I have coded according to his group. For example: If a user is associated with the 'ocassional' group then he should be shown the price as , say, 50 bucks and if a user is associated with the 'regular' group then he should be shown the price as, say, 40 bucks I can easily do this by coding a single snippet for every product's variant, but there are a lot of variants (more than 100 and growing). I have created a resource(page) for every product and it's variant. Every variant has a price. It is this price that I want to be shown according to the logged in user group membership. I hope I am able to explain my query clearly. Please help me do this functionality. Thanks

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  • 3d symmetry search algorithm

    - by aaa
    this may be more appropriate for math overflow, but nevertheless: Given 3d structure (for example molecule), what is a good approach/algorithm to find symmetry (rotational/reflection/inversion/etc.)? I came up with brute force naive algorithm, but it seems there should be better approach. I am not so much interested in genetic algorithms as I would like best symmetry rather then almost the best symmetry link to website/paper would be great. thanks

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  • client-server syncing methodology [theoretical]

    - by Kenneth Ballenegger
    I'm in the progress of building an web-app that syncs with an iOS client. I'm currently tackling trying to figure out how to go about about syncing. I've come up with following two directions: I've got a fairly simple server web-app with a list of items. They are ordered by date modified and as such syncing the order does not matter. One direction I'm considering is to let the client deal with syncing. I've already got an API that lets the client get the data, as well as do certain actions on it, such as update, add or remove single items. I was considering: 1) on each sync asking the server for all items modified since the last successful sync and updating the local records based on what's returned by the server, and 2) building a persistent queue of create / remove / update requests on the client, and keeping them until confirmation by the server. The risk with this approach is that I'm basically asking each side to send changes to the other side, hoping it works smoothly, but risking a diversion at some point. This would probably be more bandwidth-efficient, though. The other direction I was considering was a more traditional model. I would have a "sync" process in which the client would send its whole list to the server (or a subset since last modified sync), the server would update the data on the server (by fixing conflicts by keeping the last modified item, and keeping deleted items with a deleted = 1 field), and the server would return an updated list of items (since last successful sync) which the client would then replace its data with. Thoughts?

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  • how to get out information from datagridview ???

    - by ghost_j1
    hi everyone I am working on program that calculate the GBA for university student in visual c# So i make an datagridview that contain columns for each subject and its mark as later and number but after the user "student" insert his subject i want to let him to press button that get the mark and the number of the cirdit hours of each subject and calculate the GBA for the student and put the result in textbox... does anyone can help me to do it ???

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  • Drupal timezone information

    - by Sebastian Hoitz
    In my drupal installation I can get the offset from UTC in seconds to the timezone I specified in the admin panel using variable_get('date_default_timezone', 0) However, now that we have daylight-saving-time, the time I get is always off by one hour. Is there a way to retrieve the actual timezone string from Drupal, as "Europe/Berlin" for example? The reason is, that I have to use this with Zend Framework's Zend_Date, but Drupal does not set the PHP default timezone, as echo date_default_timezone_get(); gives me System/Localtime.

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  • SQL query using information from 4 tables (not all directly linked)

    - by Yvonne
    I'm developing a simple classroom system, where teachers manage classes and their subjects. I have 2 levels of access in my teachers table, assigned by an integer (1 = admin, 2 = user)... Meaning that the headteacher is the admin :) A teacher (of level 1) can have have many classes and a class can have many teachers (so I have 'TeachersClasses' table). A class can have many subjects, and a teacher can have many subjects. Basically, I'm attempting a query to display the admin teacher's (level 1) subjects. However, only teachers with a level of 2, are directly related to a subject, which is set by the admin user. The headteacher can view all of their subjects via the classroom, but I cannot get all of the subjects to be displayed on one page, instead I can only get the subjects to appear under a specific classroom right now... This is what I have so far, which is returning nothing. (I'm guessing this may require an SQL clause more advanced that 'INNER JOIN' which is the only join type I am familiar with, and thought it would be enough! $query = "SELECT subjects.subjectid, subjects.subjectname, subjects.subjectdetails, classroom.classid, classroom.classname FROM subjects INNER JOIN classroom ON subjects.subjectid = classroom.classid INNER JOIN teacherclasses ON classroom.classid = teacherclasses.classid INNER JOIN teachers ON teacherclasses.teacherid = teachers.teacherid WHERE teachers.teacherid = '".intval( $_SESSION['SESS_TEACHERID'] )."'"; In order for all subjects related to the headteachers class to be displayed, I'm gathering that all of my tables will need to be called up here? Thanks for any help! Example output: subject name: maths // teacher: mr smith // classroom: DG99 x10 for all the subjects associated with the headteachers classrooms :)

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  • Producing POD summary information in HTML

    - by justintime
    Is there a tool available that can produce an HTML summary list of perl modules or scripts in a directory tree. Given =head1 NAME wibble.pl - does wibble actions I would like to see something like <a href="docsforwibble">wibble.pl</a> - does wibble actions <a href="docsforwobble">wibble.pl</a> - does wobble actions

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  • Complex behavior generated by simple computation

    - by Yuval A
    Stephen Wolfram gave a fascinating talk at TED about his work with Mathematica and Wolfram Alpha. Amongst other things, he pointed out how very simple computations can yield extremely complex behaviors. (He goes on to discuss his ambition for computing the entire physical universe. Say what you will, you gotta give the guy some credit for his wild ideas...) As an example he showed several cellular automata. What other examples of simple computations do you know of that yield fascinating results?

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  • How to draw a graph in LaTeX?

    - by Amir Rachum
    First of all, let me say I'm using LyX, though I have no problem using ERT. Secondly, what is the most simplest way to draw a simple graph like this in Latex? I've seen some documents with graphs and I've seen some examples, but I couldn't figure out how to just draw a simple graph - what packages do I need, etc?

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  • Getting memory section information

    - by Basilevs
    Can somebody explain me how the following code works? # if defined(__ELF__) # define __SECTION_FLAGS ", \"aw\" , @progbits" /* writable flag needed for ld ".[cd]tors" sections bug workaround) */ # elif defined(__COFF__) # define __SECTION_FLAGS ", \"dr\"" /* untested, may be writable flag needed */ # endif asm ( ".section .ctors" __SECTION_FLAGS "\n" ".globl __ctors_begin__\n" "__ctors_begin__:\n" ".previous\n" ); asm /* ld ".[cd]tors" sections bug workaround */ ( ".section .ctors0" __SECTION_FLAGS "\n" ".globl __ctors0_begin__\n" "__ctors0_begin__:\n" ".previous\n" ); Similarly we are getting __ctors_end__ , __ctors0_end__ and destructors location is also obtained this way. After some ld bug workarounds all functions pointed by pointers from __ctors_begin__ to __ctors_end__ are executed. I don't know assembler and this code is impossible for me to interpret. BTW: I know that invoking C++ contructors/destructors from C is not a task to be considered safe or easy.

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  • Provable planarity of flowcharts

    - by Nikolaos Kavvadias
    Hi all I have a question: is there any reference (e.g. paper) with a proof of the planarity of flowchart layouts? Can anyone suggest an algorithm for generating flowchart (planar) layouts? I know that there are some code-to-flowchart tools out there, but i'm unaware of their internals. Thanks in advance -kavi

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  • Cannot modify header information - headers already sent by

    - by bhaskaragr29
    <?php //require_once 'wordwrap.php'; //$text="Lorem Ipsum Lorem Ipsum Lorem Ipsum Lorem Ipsum Lorem Ipsum Lorem Ipsum Lorem Ipsum Lorem Ipsum Lorem Ipsum"; $im=imagecreatefrompng('testing.png'); //$arr=word($text); $white = imagecolorallocate($im,255,255,255); $font='arial.ttf'; $m=121; for($i=0;$i<sizeof($arr);$i++) { imagettftext($im,25,11,124,'Hello world!', $white); } header('Content-type: image/png'); imagepng($im); imagedestroy($im); ?> I am getting error..please help me on this.

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  • How to minimize total cost of shortest path tree

    - by Michael
    I have a directed acyclic graph with positive edge-weights. It has a single source and a set of targets (vertices furthest from the source). I find the shortest paths from the source to each target. Some of these paths overlap. What I want is a shortest path tree which minimizes the total sum of weights over all edges. For example, consider two of the targets. Given all edge weights equal, if they share a single shortest path for most of their length, then that is preferable to two mostly non-overlapping shortest paths (fewer edges in the tree equals lower overall cost). Another example: two paths are non-overlapping for a small part of their length, with high cost for the non-overlapping paths, but low cost for the long shared path (low combined cost). On the other hand, two paths are non-overlapping for most of their length, with low costs for the non-overlapping paths, but high cost for the short shared path (also, low combined cost). There are many combinations. I want to find solutions with the lowest overall cost, given all the shortest paths from source to target. Does this ring any bells with anyone? Can anyone point me to relevant algorithms or analogous applications? Cheers!

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  • Can Haskell's Parsec library be used to implement a recursive descent parser with backup?

    - by Thor Thurn
    I've been considering using Haskell's Parsec parsing library to parse a subset of Java as a recursive descent parser as an alternative to more traditional parser-generator solutions like Happy. Parsec seems very easy to use, and parse speed is definitely not a factor for me. I'm wondering, though, if it's possible to implement "backup" with Parsec, a technique which finds the correct production to use by trying each one in turn. For a simple example, consider the very start of the JLS Java grammar: Literal: IntegerLiteral FloatingPointLiteral I'd like a way to not have to figure out how I should order these two rules to get the parse to succeed. As it stands, a naive implementation like this: literal = do { x <- try (do { v <- integer; return (IntLiteral v)}) <|> (do { v <- float; return (FPLiteral v)}); return(Literal x) } Will not work... inputs like "15.2" will cause the integer parser to succeed first, and then the whole thing will choke on the "." symbol. In this case, of course, it's obvious that you can solve the problem by re-ordering the two productions. In the general case, though, finding things like this is going to be a nightmare, and it's very likely that I'll miss some cases. Ideally, I'd like a way to have Parsec figure out stuff like this for me. Is this possible, or am I simply trying to do too much with the library? The Parsec documentation claims that it can "parse context-sensitive, infinite look-ahead grammars", so it seems like something like I should be able to do something here.

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