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  • Given a vector of maximum 10 000 natural and distinct numbers, find 4 numbers(a, b, c, d) such that

    - by king_kong
    Hi, I solved this problem by following a straightforward but not optimal algorithm. I sorted the vector in descending order and after that substracted numbers from max to min to see if I get a + b + c = d. Notice that I haven't used anywhere the fact that elements are natural, distinct and 10 000 at most. I suppose these details are the key. Does anyone here have a hint over an optimal way of solving this? Thank you in advance! Later Edit: My idea goes like this: '<<quicksort in descending order>>' for i:=0 to count { // after sorting, loop through the array int d := v[i]; for j:=i+1 to count { int dif1 := d - v[j]; int a := v[j]; for k:=j+1 to count { if (v[k] > dif1) continue; int dif2 := dif1 - v[k]; b := v[k]; for l:=k+1 to count { if (dif2 = v[l]) { c := dif2; return {a, b, c, d} } } } } } What do you think?(sorry for the bad indentation)

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  • What is the best PHP MYSQL wrapper?

    - by Jestro
    I've bounced around between different wrappers, my own, and using straight php mysql functions over the years but I'm sure there's a really good solution out there. What is it? :) EDIT: Only needs to connect to MYSQL and it would be nice if it was lightweight.

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  • cakephp find('list') - problem using

    - by MOFlint
    I'm trying to get an array to poplulate a Counties select. If I use find('all') I can get the data but this array needs flattening to use in the view with $form-input($counties). If I use find('list') I can't seem to get the right array - which is simple array of county names. What I have tried is this: $ops=array( 'conditions' => array( 'display' => '!=0', 'TO_DAYS(event_finish) >= TO_DAYS(NOW())' ), 'fields' => 'DISTINCT venue_county', 'order' => 'venue_county DESC' ); $this->set('counties', $this->Event->find('list',$ops)); but the SQL this generates is: SELECT Event.id, DISTINCT Event.venue_county FROM events AS Event WHERE display = 1 AND TO_DAYS(event_finish) = TO_DAYS(NOW()) ORDER BY venue_county DESC which generates an error because it first inserts the Event.id field in the query - which is not wanted and causes the error. In my database I have a single table for Events which includes the venue address and I don't really want to create another table for address. What options should I be using efor the find('list') call?

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  • Is C really a subset of C++?

    - by Allopen
    What I mean is, can any C code be implemented via C++? Maybe just simply change a compiler? I know C is much more efficient and concise. But despite of these, can C++ used to implement all functions that are implemented by C?

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  • Find existence of number in a sorted list in constant time? (Interview question)

    - by Rich
    I'm studying for upcoming interviews and have encountered this question several times (written verbatim) Find or determine non existence of a number in a sorted list of N numbers where the numbers range over M, M N and N large enough to span multiple disks. Algorithm to beat O(log n); bonus points for constant time algorithm. First of all, I'm not sure if this is a question with a real solution. My colleagues and I have mused over this problem for weeks and it seems ill formed (of course, just because we can't think of a solution doesn't mean there isn't one). A few questions I would have asked the interviewer are: Are there repeats in the sorted list? What's the relationship to the number of disks and N? One approach I considered was to binary search the min/max of each disk to determine the disk that should hold that number, if it exists, then binary search on the disk itself. Of course this is only an order of magnitude speedup if the number of disks is large and you also have a sorted list of disks. I think this would yield some sort of O(log log n) time. As for the M N hint, perhaps if you know how many numbers are on a disk and what the range is, you could use the pigeonhole principle to rule out some cases some of the time, but I can't figure out an order of magnitude improvement. Also, "bonus points for constant time algorithm" makes me a bit suspicious. Any thoughts, solutions, or relevant history of this problem?

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  • How is <tgmath.h> implemented?

    - by sync
    C doesn't have (to the best of my knowledge) overloading or templates, right? So how can a set of type-agnostic functions with the same name exist in plain ol' C? The usual compile-time trickery would involve a whole bunch of macros, wouldn't it?

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  • Problem Initializing an Array Of Structs

    - by FallSe7en
    I am trying to initialize the following array of the following struct, but my code isn't compiling. Can anybody help me out? The struct/array: struct DiningCarSeat { int status; int order; int waiterNum; Lock customerLock; Condition customer; DiningCarSeat(seatNum) { char* tempLockName; sprintf(tempLockName, "diningCarSeatLock%d", seatNum); char* tempConditionName; sprintf(tempConditionName, "diningCarSeatCondition%d", seatNum); status = 0; order = 0; waiterNum = -1; customerLock = new Lock(tempLockName); customer = new Condition(tempConditionName); } } diningCarSeat[DINING_CAR_CAPACITY]; The relevant errors: ../threads/threadtest.cc: In constructor `DiningCarSeat::DiningCarSeat(int)': ../threads/threadtest.cc:58: error: no matching function for call to `Lock::Lock()' ../threads/synch.h:66: note: candidates are: Lock::Lock(const Lock&) ../threads/synch.h:68: note: Lock::Lock(char*) ../threads/threadtest.cc:58: error: no matching function for call to `Condition::Condition()' ../threads/synch.h:119: note: candidates are: Condition::Condition(const Condition&) ../threads/synch.h:121: note: Condition::Condition(char*) ../threads/threadtest.cc:63: error: expected primary-expression before '.' token ../threads/threadtest.cc:64: error: expected primary-expression before '.' token ../threads/threadtest.cc: At global scope: ../threads/threadtest.cc:69: error: no matching function for call to `DiningCarSeat::DiningCarSeat()' ../threads/threadtest.cc:51: note: candidates are: DiningCarSeat::DiningCarSeat(const DiningCarSeat&) ../threads/threadtest.cc:58: note: DiningCarSeat::DiningCarSeat(int) Thanks in advance!

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  • Problem with C++ classes

    - by Mike
    I have a class defined called extBlock. I then make an instance of that class with this extBlock mainBlock = new extBlock(1, 1024); I get this error: error C2440: 'initializing' : cannot convert from 'extBlock *' to 'extBlock' Can anyone help me with why I am getting this error. I have seen examples online of declaring it like this with a pointer extBlock *mainBlock = new extBlock(1, 1024); But if I do it this way it does not let me call the functions of mainBlock

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  • Oracle: Difference in execution plans between databases

    - by Will
    Hello, I am comparing queries my development and production database. They are both Oracle 9i, but almost every single query has a completely different execution plan depending on the database. All tables/indexes are the same, but the dev database has about 1/10th the rows for each table. On production, the query execution plan it picks for most queries is different from development, and the cost is somtimes 1000x higher. Queries on production also seem to be not using the correct indexes for queries in some cases (full table access). I have ran dbms_utility.analyze schema on both databases recently as well in the hopes the CBO would figure something out. Is there some other underlying oracle configuration that could be causing this? I am a developer mostly so this kind of DBA analysis is fairly confusing at first..

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  • Lucene boost: I need to make it work better

    - by zvikico
    I'm using Lucene to index components with names and types. Some components are more important, thus, get a bigger boost. However, I cannot get my boost to work properly. I sill get some components appear later (get worse score), even though they have a higher boost. Note that the indexing is done on one field only and I've set the boost to that field alone. I'm using Lucene in Java. I don't think it has anything to do with the field length. I've seen components with the same name (but different type) get the wrong score.

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  • Is it possible to slice off the end of a URL with XSLT 1.0?

    - by Eric
    Title says it all really. Using only XSLT 1.0's string functions, how would I go about slicing off the end of a url? So from http://stackoverflow.com/questions/2981175/is-it-possible-to-slice-the-end-of-a-url-with-xslt-1-0 I would like to extract is-it-possible-to-slice-the-end-of-a-url-with-xslt-1-0 Is this possible?

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  • endpoints (bug?) behavior in xts

    - by Alex
    If I try to get endpoints for every year, for example, and do the following: xts.data <- xts(1:10000, order.by=seq(from=as.Date("1970-01-01"), by=1, len=10000)) z <- endpoints(xts.data, on="months", k=12) The return value for this is: > z [1] 0 10000 Same with numbers higher than 12. Why would xts simply not return indices of every year or 13th month starting from the beginning. Is it limited by the number of periods in a year? That is if i did: z <- endpoints(xts.data, on="weeks", k=54) This seems to work fine.

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  • Where can I learn web programming from start to mastery?

    - by user353046
    I tried doing tutorials but it is unorganized and unstructured, where can I learn PHP from beginner to master? I'm looking for a site like www.w3chools.com, but somehow I feel it is incomplete, specially when it comes to more advanced functions. I know some basics but I wouldn't be able to for example make a secure online webstore, and I seem to be stuck at this point, how / where should I proceed?

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  • Play Framework Form "fold" method naming rationale

    - by oym
    Play Framework's (2.x) Form class has a method called fold who's usage is indicated as: anyForm.bindFromRequest().fold( f => redisplayForm(f), t => handleValidFormSubmission(t) ) Essentially, the first function parameter is what gets executed on binding failure, and the 2nd on binding success. To me it seems similar to the 'success' and 'error' callbacks of jquery's ajax function. My question is why did the Play developers call the method "fold"? As a disclaimer I am new to Scala, but I am failing to see the connection between this and the functional Scala fold operation. The only similarity is that it is a higher order function; but I don't see any combining that is taking place, nor does it delegate internally in its implementation to any of the Scala fold functions.

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  • Script to parse emails for attachments

    - by Swanny
    I am looking for a way to monitor a Linux mbox email account, when an email arrives I would like to download an attachment from the email and save the attachment (CSV file) so that it may be used by a PHP script. What would be the best way of going about this? I have looked at PHP's IMAP functions but this does not appear to be the most appropriate method when a simple bash script may be all that is required?

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  • What is your most useful C/C++ utility?

    - by maddizzyro
    It seems that every project has an "utility" module with various code snippets used throughout other files and which don't fit any particular pattern. What utility classes, functions, and macros do you find most useful in your C/C++ projects? Please keep the entries small (under 100 lines) and give only one example per post.

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  • purpose of php consutructor

    - by Bharanikumar
    Hi , Am working in the classes and object class structure , but not extream level , Just class and function , then in one place instantiation . that's it , not much big functions like __construct etc , Please tell me very simply , 1.what is th purpose of constructor ad destructor , But i know theoretical explanation school level , But i am expecting something like in real time , which situation we have to use, and is there any example for that please tell me, Regards

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  • Purpose of PHP constructors

    - by Bharanikumar
    Hi, I am working with classes and object class structure, but not at a complex level – just classes and functions, then, in one place, instantiation. As to __construct and __destruct, please tell me very simply: what is the purpose of constructors and destructors? I know the school level theoretical explanation, but i am expecting something like in real world, as in which situations we have to use them. Provide also an example, please. Regards

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  • Why would ftp_connect() fail on production server if it works elsewhere for connecting to the same F

    - by letseatfood
    I have a script that uses ftp_connect() among other FTP PHP functions for uploading a file. ftp_connect() works when executed on my local development server for connecting to a remote FTP server. The same script, when executed on the remote server does not work for connecting to the exact same FTP server. Could somebody please point me in the right direction? Thanks!

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