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  • How do we achieve "substring-match" under O(n) time?

    - by Pacerier
    I have an assignment that requires reading a huge file of random inputs, for example: Adana Izmir Adnan Menderes Apt Addis Ababa Aden ADIYAMAN ALDAN Amman Marka Intl Airport Adak Island Adelaide Airport ANURADHAPURA Kodiak Apt DALLAS/ADDISON Ardabil ANDREWS AFB etc.. If I specify a search term, the program is supposed to find the lines whereby a substring occurs. For example, if the search term is "uradha", the program is supposed to show ANURADHAPURA. If the search term is "airport", the program is supposed to show Amman Marka Intl Airport, Adelaide Airport A quote from the assignment specs: "You are to program this application taking efficiency into account as though large amounts of data and processing is involved.." I could easily achieve this functionality using a loop but the performance would be O(n). I was thinking of using a trie but it seems to only work if the substring starts from index 0. I was wondering what solutions are there which gives a performance better than O(n)?

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  • How do API Keys and Secret Keys work?

    - by viatropos
    I am just starting to think about how api keys and secret keys work. Just 2 days ago I signed up for Amazon S3 and installed the S3Fox Plugin. They asked me for both my Access Key and Secret Access Key, both of which require me to login to access. So I'm wondering, if they're asking me for my secret key, they must be storing it somewhere right? Isn't that basically the same thing as asking me for my credit card numbers or password and storing that in their own database? How are secret keys and api keys supposed to work? How secret do they need to be? Are these applications that use the secret keys storing it somehow? Thanks for the insight.

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  • Math - Adding with PHP

    - by Wayne
    Basically I can't get it right. I need something like this: if($p == 1) { $start = 0; $limit = 16; } The numbers must add on depending on the value of the $p, e.g. if $p is 5 then the values of $start and $limit would be: if($p == 5) { $start = 64; $limit = 80; } The math is to add 16, depending on the value of $p. Thanks.

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  • Optimal Sharing of heavy computation job using Snow and/or multicore

    - by James
    Hi, I have the following problem. First my environment, I have two 24-CPU servers to work with and one big job (resampling a large dataset) to share among them. I've setup multicore and (a socket) Snow cluster on each. As a high-level interface I'm using foreach. What is the optimal sharing of the job? Should I setup a Snow cluster using CPUs from both machines and split the job that way (i.e. use doSNOW for the foreach loop). Or should I use the two servers separately and use multicore on each server (i.e. split the job in two chunks, run them on each server and then stich it back together). Basically what is an easy way to: 1. Keep communication between servers down (since this is probably the slowest bit). 2. Ensure that the random numbers generated in the servers are not highly correlated.

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  • encoding of =1 in emails

    - by Maenny
    Hi folks, I have probably a stupid problem. In a script I generate a URL with GET parameters, something like 'www.mydomain.com/index.php?item=1234'. This URL will be sent by PHP through mail() in an UTF-8 encoding (the scriptfile itself also is utf-8). Now each time I have the GET-Parameter with two numbers after the '=' the URL in the email looks like 'www.mydomain.com/index.php?item?34' with a rectangle instead of '=12'. I am sure there is an easy way to fix this? Thanks in advance, Maenny

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  • Tools to document/visualize call graph?

    - by Dave Griffiths
    Hi, having recently joined a project with a vast amount of code to get to grips with, I would like to start documenting and visualizing some of the flows through the call graph to give me a better understanding of how everything fits together. This is what I would like to see in my ideal tool: every node is a function/method nodes are connected if one function can call another optional square box in between detailing conditions under which call is made (or a label icon you can hover over like a tooltip) also icon on edge describing parameters hover over node and description is displayed optional icons for node to display pseudo code scenario/domain view - display subset of complete diagram for particular use-case slide view mode - for each frame, the currently executing function is highlighted plenty of options over what to display to reduce on-screen clutter the interactive use of such a tool is key, I'm not looking for a Graphviz type solution because there would be too much clutter. The ability to form a view of a subset of the entire graph would be very handy (maybe with the unimportant clutter greyed out). Don't need automatic generation from source code, happy to enter it manually. Almost like a mind-map. Does that make sense? If you are not aware of such a tool, do you also think it would be useful? (Just in case I decide to go and scratch that itch one day!)

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  • How do I modify this download function in Python?

    - by TIMEX
    Right now, it's iffy. Gzip, images, sometimes it doesn't work. How do I modify this download function so that it can work with anything? (Regardless of gzip or any header?) How do I automatically "Detect" if it's gzip? I don't want to always pass True/False, like I do right now. def download(source_url, g = False, correct_url = True): try: socket.setdefaulttimeout(10) agents = ['Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0)','Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.1)','Microsoft Internet Explorer/4.0b1 (Windows 95)','Opera/8.00 (Windows NT 5.1; U; en)'] ree = urllib2.Request(source_url) ree.add_header('User-Agent',random.choice(agents)) ree.add_header('Accept-encoding', 'gzip') opener = urllib2.build_opener() h = opener.open(ree).read() if g: compressedstream = StringIO(h) gzipper = gzip.GzipFile(fileobj=compressedstream) data = gzipper.read() return data else: return h except Exception, e: return ""

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  • Regex gurus! here's a teaser: mixed thousands separators and csv's

    - by chichilatte
    I've got a string like... "labour 18909, liberals 12,365,conservatives 14,720" ...and i'd like a regex which can get rid of any thousands separators so i can pull out the numbers easily. Or even a regex which could give me a tidy array like: (labour => 18909, liberals => 12365, conservatives => 14720) Oh i wish i had the time to figure out regexes! Maybe i'll buy one as a toilet book, mmm.

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  • JavaScript on Android randomly stops working

    - by AndersWid
    Hi! I have an application that uses a WebView and a html-page with javascript functions. Randomly the JavaScript functions doesn't seem to be called. It works up to a random point (I have looked at this bug all day) can only be produced on hardware (HTC Legend) not on emulator. Basicly I'm using callback to javaScript whenever the user presses a button, these callbacks tell the html to redraw using javaScript functions. mHandler.post(new Runnable() { public void run() { mWebView.loadUrl("javascript:getDataLine()"); } }); The first line in this javaScript code is an alert that says that it has started, so that I can see that it's working. Settings alerts or console.log's everywhere won't help as it seems the problem is in the webview or in Android itself. I need a way to see what's going on in the background. Maybe see if a previous call failed and stalled the thread or something.

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  • update columns when value is numeric in tsql

    - by knittl
    i want to normalize date fields from an old badly designed db dump. i now need to update every row, where the datefield only contains the year. update table set date = '01.01.' + date where date like '____' and isnumeric(date) = 1 and date >= 1950 but this will not work, because sql does not do short circuit evaluation of boolean expressions. thus i get an error "error converting nvarchar '01.07.1989' to int" is there a way to work around this? the column also contains strings with a length of 4, which are not numbers (????, 5/96, 70/8, etc.) the table only has 60000 rows

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  • Html combo box to database record Id

    - by LanguaFlash
    I'm fairly sure there has to be a simple solution to my problem, but I am a new web developer and can't quite figure it out. On my page I have a combo box whose values are filled from my database. When the user submits the form, how to I go about converting those values back to the record numbers in the database? Up to now I have been just doing a sort of reversed lookup in my database to try to get the record's ID. This has quite a few obvious flaws and I am sure that there has to be a better way. I am used to MS Forms combo boxes where the record data and ID are never separated. But in the case of a web form, I have no way to do multiple columns in the combo box like I am used to. Thanks! Jeff

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  • Centralizing a floating element :(

    - by 2x2p1p
    Hi guys :| My "div" element have a relative width, it isn't absolute so I can't use exact numbers to centralize. A nice solution is to use "display: inline-block": body { text-align: center; } #myDiv { border: 1px solid black; display: inline-block; padding: 50px; } But this element NEEDS to float, I tried this: #myDiv { border: 1px solid black; display: inline-block; float: left; padding: 50px; } And this: #myDiv { border: 1px solid black; display: inline-block; padding: 50px; position: absolute; } Without any success, can somebody help me ? Thanks

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  • search paths where one native library depends on another

    - by carneades
    I'm using JNA and Java but I think this question affects any native-to-nonnative bridge. I have a Java application which relies on lib1.dylib, and lib1.dylib relies on lib2.dylib. I want to put everything inside of my .app file on Mac. I can easily put lib1.dylib inside and set java.classpath (or NativeLibrary.addSearchPath()) to tell the JVM where to find lib1.dylib. The trouble is, I don't know how to communicate that lib1.dylib's dependencies are also in the location I provided. The result is that lib1 is loaded fine, but then lib2 can't be found since it's not in the operating system's library path. Anyone know how I can overcome this problem? I imagine it must come up plenty in big projects with large numbers of shared libraries.

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  • Php is stripping one letter "g" from my rtrim function but not other chars

    - by Chase
    I'm trying to trim some youtube URLs that I am reading in from a playlist. The first 3 work fine and all their URLs either end in caps or numbers but this one that ends in a lower case g is getting trimmed one character shorter than the rest. for ($z=0; $z <= 3; $z++) { $ythref2 = rtrim($tubeArray["feed"]["entry"][$z]["link"][0]["href"], '&feature=youtube_gdata'); The URL is http://www.youtube.com/watch?v=CuE88oVCVjg&feature=youtube_gdata .. and it should get trimmed down to .. http://www.youtube.com/watch?v=CuE88oVCVjg but instead it is coming out as http://www.youtube.com/watch?v=CuE88oVCVj. I think it may be the ampersand symbol but I am not sure.

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  • Reading files from an embedded ZIP archive

    - by aix
    I have a ZIP archive that's embedded inside a larger file. I know the archive's starting offset within the larger file and its length. Are there any Java libraries that would enable me to directly read the files contained within the archive? I am thinking along the lines of ZipFile.getInputStream(). Unfortunately, ZipFile doesn't work for this use case since its constructors require a standalone ZIP file. For performance reasons, I cannot copy the ZIP achive into a separate file before opening it. edit: Just to be clear, I do have random access to the file.

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  • Multiplying char and int together in C part 2

    - by teehoo
    If I do the following: int c0 = CHAR_MAX; //8 bit int c1 = CHAR_MAX; //8-bit int i = c0*c1; //store in 32-bit variable printf("%d\n", i); //prints 16129 We can see that there is no problem with to 8-bit numbers being multiplied together, and producing a 32-bit output. However, if I do int i0 = INT_MAX; //32-bit int i1 = INT_MAX; //32 bit variable long long int ll = i0*i1; //store in 64-bit variable printf("%lld\n", ll); //prints 1..overflow!! In this case, two 32-bit variables were multiplied together, overflowed, and then were assigned to the 64-bit variable. So why did this overflow happen when multiplying the ints, but not the chars? Is it dependent on the default word-size of my machine? (32-bits)

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  • Avoiding a fork()/SIGCHLD race condition

    - by larry
    Please consider the following fork()/SIGCHLD pseudo-code. // main program excerpt for (;;) { if ( is_time_to_make_babies ) { pid = fork(); if (pid == -1) { /* fail */ } else if (pid == 0) { /* child stuff */ print "child started" exit } else { /* parent stuff */ print "parent forked new child ", pid children.add(pid); } } } // SIGCHLD handler sigchld_handler(signo) { while ( (pid = wait(status, WNOHANG)) > 0 ) { print "parent caught SIGCHLD from ", pid children.remove(pid); } } In the above example there's a race-condition. It's possible for "/* child stuff */" to finish before "/* parent stuff */" starts which can result in a child's pid being added to the list of children after it's exited, and never being removed. When the time comes for the app to close down, the parent will wait endlessly for the already-finished child to finish. One solution I can think of to counter this is to have two lists: started_children and finished_children. I'd add to started_children in the same place I'm adding to children now. But in the signal handler, instead of removing from children I'd add to finished_children. When the app closes down, the parent can simply wait until the difference between started_children and finished_children is zero. Another possible solution I can think of is using shared-memory, e.g. share the parent's list of children and let the children .add and .remove themselves? But I don't know too much about this. EDIT: Another possible solution, which was the first thing that came to mind, is to simply add a sleep(1) at the start of /* child stuff */ but that smells funny to me, which is why I left it out. I'm also not even sure it's a 100% fix. So, how would you correct this race-condition? And if there's a well-established recommended pattern for this, please let me know! Thanks.

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  • function to find common rows between more than two data frames in R

    - by biohazard
    I have 4 data frames, and would like to find the rows whose values in a certain column do not exist in any of the other data frames. I wrote this function: #function to test presence of $Name in 3 other datasets common <- function(a, b, c, d) { is.B <- is.numeric(a$Name %in% b$Name) == 1 is.C <- is.numeric(a$Name %in% c$Name) == 1 is.D <- is.numeric(a$Name %in% d$Name) == 1 t <- as.numeric(is.B & is.C & is.D) t } However, the output is always t = 0. This means that it tells me that there are no unique rows in any data sets, even though the datas frames have very different numbers of rows. Since there are no duplicate rows in any of the data frames, I should be getting t = 1 for at least some rows in the biggest dataset. Can someone figure out what I got wrong?

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  • how to click on a button in python

    - by Ciobanu Alexandru
    Trying to build some bot for clicking "skip-ad" button on a page. So far, i manage to use Mechanize to load a web-driver browser and to connect to some page but Mechanize module do not support js directly so now i need something like Selenium if i understand correct. I am also a beginner in programming so please be specific. How can i use Selenium or if there is any other solution, please explain details. This is the inner html code for the button: <a id="skip-ad" class="btn btn-inverse" onclick="open_url('http://imgur.com/gallery/tDK9V68', 'go'); return false;" style="font-weight: bold; " target="_blank" href="http://imgur.com/gallery/tDK9V68"> … </a> And this is my source so far: #!/usr/bin/python # FILENAME: test.py import mechanize import os, time from random import choice, randrange prox_list = [] #list of common UAS to apply to each connection attempt to impersonate browsers user_agent_strings = [ 'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1468.0 Safari/537.36', 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.1) Gecko/2008071615 Fedora/3.0.1-1.fc9 Firefox/3.0.1', 'Opera/9.80 (Windows NT 6.0) Presto/2.12.388 Version/12.14', 'Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/11.52', 'Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:23.0) Gecko/20131011 Firefox/23.0', 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; Media Center PC 6.0; InfoPath.3; MS-RTC LM 8; Zune 4.7', 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET CLR 2.0.50727; SLCC2; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; Zune 4.0; Tablet PC 2.0; InfoPath.3; .NET4.0C; .NET4.0E)', 'Mozilla/5.0 (compatible; MSIE 10.6; Windows NT 6.1; Trident/5.0; InfoPath.2; SLCC1; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 2.0.50727) 3gpp-gba UNTRUSTED/1.0', 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.0; Trident/5.0; chromeframe/11.0.696.57)', 'Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; InfoPath.1; SV1; .NET CLR 3.8.36217; WOW64; en-US)', 'Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; GTB7.4; InfoPath.2; SV1; .NET CLR 3.3.69573; WOW64; en-US)' ] def load_proxy_list(target): #loads and parses the proxy list file = open(target, 'r') count = 0 for line in file: prox_list.append(line) count += 1 print "Loaded " + str(count) + " proxies!" load_proxy_list('proxies.txt') #for i in range(1,(len(prox_list) - 1)): # depreceated for overloading for i in range(1,30): br = mechanize.Browser() #pick a random UAS to add some extra cover to the bot br.addheaders = [('User-agent', choice(user_agent_strings))] print "----------------------------------------------------" #This is bad internet ethics br.set_handle_robots(False) #choose a proxy proxy = choice(prox_list) br.set_proxies({"http": proxy}) br.set_debug_http(True) try: print "Trying connection with: " + str(proxy) #currently using: BTC CoinURL - Grooveshark Broadcast br.open("http://cur.lv/4czwj") print "Opened successfully!" #act like a nice little drone and view the ads sleep_time_on_link = randrange(17.0,34.0) time.sleep(sleep_time_on_link) except mechanize.HTTPError, e: print "Oops Request threw " + str(e.code) #future versions will handle codes properly, 404 most likely means # the ad-linker has noticed bot-traffic and removed the link # or the used proxy is terrible. We will either geo-locate # proxies beforehand and pick good hosts, or ditch the link # which is worse case scenario, account is closed because of botting except mechanize.URLError, e: print "Oops! Request was refused, blacklisting proxy!" + str(e) prox_list.remove(proxy) del br #close browser entirely #wait between 5-30 seconds like a good little human sleep_time = randrange(5.0, 30.0) print "Waiting for %.1f seconds like a good bot." % (sleep_time) time.sleep(sleep_time)

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  • Efficient synchronization of querying an array of resources

    - by Erel Segal Halevi
    There is a list of N resources, each of them can be queried by at most a single thread at a time. There are serveral threads that need to do the same thing at approximately the same time: query each of the resources (each thread has a different query), in arbitrary order, and collect the responses. If each thread loops over the resources in the same order, from 0 to N-1, then they will probably have to wait for each other, which is not efficient. I thought of letting the threads loop over the resources in a random permutation, but this seems too complex and also not so efficient, for example, for 2 resources and 2 threads, in half the cases they will choose the same order and wait for each other. Is there a simple and more efficient way to solve this?

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  • Formatting a query to enumerate through 2 different datatables

    - by boiler1974
    I have 2 datatables sendTable and recvTable They both have identical column names and numbers of columns "NODE" "DSP Name" "BUS" "IDENT" "STATION" "REF1" "REF2" "REF3" "REF4" "REF5" "REF6" "REF7" "REF8" I need to compare these 2 tables and separate out the mismatches I only need to check Columns 3-11 and Ignore col 1 and 2 I tried at first removing the 2 columns and then loop thru row by row and return matches and mismatches but the problem with this approach is that I no longer have the "NODE" and "DSP Name" associated with the row when I finalize my results So I need help with a query Here is my attempt var samerecordQuery = from r1 in sendTable.AsEnumerable() where r1.Field<int>("BUS").Equals(from r2 in recvTable.AsEnumerable() where r2.Field<int>("BUS")) this obviously doesn't work so how do I format the query to say from r1 cols[3-11] equals r2 cols [3-11] and once I have this I can use the except to pull out the mismatches

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  • Understanding The Convolution Matrix

    - by Ryan Naddy
    I am learning about the Convolution Matrix, and I understand how they work, but I don't understand how to know before hand what the output of a Matrix will look like. For example lets say I want to add a blur to an image, I could guess 10,000+ different combinations of numbers before I get the correct one. I do know though that this formula will give me a blur effect, but I have no idea why. float[] sharpen = new float[] { 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f }; Can anyone either explain to me how this works or point me to some article, that explains this? I would like to know before hand what a possible output of the matrix will be without guessing. Basically I would like to know why do we put that number in the filed, and why not some other number?

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  • Why does this give a segmentation fault?

    - by nightcracker
    I'm stunned, why does this code give me a segmentation fault? #include <stdio.h> #define LIMIT 1500000 typedef struct { int p; int a; int b; } triplet; int main(int argc, char **argv) { int i; triplet triplets[LIMIT]; for (i = 0; i < 5; i++) { triplets[i].p = 9; // remove this line and everything works fine } printf("%d\n", triplets[15].p); return 0; } EDIT: After changing LIMIT to 150 I no longer get a segmentation fault, it prints random numbers instead.

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  • Subset generation by rules

    - by Sazug
    Let's say that we have a 5000 users in database. User row has sex column, place where he/she was born column and status (married or not married) column. How to generate a random subset (let's say 100 users) that would satisfy these conditions: 40% should be males and 60% - females 50% should be born in USA, 20% born in UK, 20% born in Canada, 10% in Australia 70% should be married and 30% not. These conditions are independent, that is we cannot do like this: (0.4 * 0.5 * 0.7) * 100 = 14 users that are males, born in USA and married (0.4 * 0.5 * 0.3) * 100 = 6 users that are males, born in USA and not married. Is there an algorithm to this generation?

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  • How to return arrays with the biggest elements in C#?

    - by theateist
    I have multiple int arrays: 1) [1 , 202,4 ,55] 2) [40, 7] 3) [2 , 48 ,5] 4) [40, 8 ,90] I need to get the array that has the biggest numbers in all positions. In my case that would be array #4. Explanation: arrays #2, #4 have the biggest number in 1st position, so after the first iteration these 2 arrays will be returned ([40, 7] and [40, 8 ,90]) now after comparing 2nd position of the returned array from previous iteration we will get array #4 because 8 7 and so on... Can you suggest an efficient algorithm for this? Doing with Linq will be preferable. UPDATE There is no limitation for the length, but as soon as some number in any position is greater, so this array is the biggest.

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