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  • List of fundamental data structures - what am I missing?

    - by jboxer
    I've been studying my fundamental data structures a bunch recently, trying to make sure I've got them down cold. By "fundamental", I mean the real basic ones. Fancy ones like Red-Black Trees and Bloom Filters are clearly worth knowing, but they're usually either enhancements of fundamental ones (Red-Black Trees are binary search trees with special properties to keep them balanced) or they're only useful in very specific situations (Bloom Filters). So far, I'm "fluent" in the following data structures: Arrays Linked Lists Stacks/Queues Binary Search Trees Heaps/Priority Queues Hash Tables However, I feel like I'm missing something. Are there any fundamental ones that I'm forgetting about? EDIT: Added these after posting the question Strings (suggested by catchmeifyoutry) Sets (suggested by Peter) Graphs (suggested by Nick D and aJ) B-Trees (Suggested by tloach) I'm a little on-the-fence about whether these are too fancy or not, but I think they're different enough from the fundamental structures (and important enough) to be worth studying as fundamental.

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  • How to set up my network/bridging using Apple Airport equipment?

    - by John
    I'd like to set up my network like this, and I want to make sure it's possible using the hardware I have. I think it should be... I've got my cable modem in one room. I want to plug it into an Apple Airport Express and create my wireless my wireless network here. The airport express will do the NAT and DHCP. By my TV there are a few things to be networked (Xbox and Tivo). I have an airport extreme here. I'd like to have the airport extreme join the wireless network and share the connection to the ethernet ports. Can anyone provide some assistance on the best way to configure to do this? Thanks!

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  • c# multi threaded file processing

    - by user177883
    There is a folder that contains 1000 of small text files. I aim to parse and process all of them while more files are being populated in to the folder. My intention is to multithread this operation as the single threaded prototype took 6 minutes to process 1000 files. I like to have reader and writer thread(s) as following : while the reader thread(s) are reading the files, I d like to have writer thread(s) to process them. Once the reader is started reading a file, I d like to mark it as being processed, such as by renaming it, once it s read, rename it to completed. How to approach such multithreaded application ? Is it better to use a distributed hash table or a queue? Which data structure to use that would avoid locks? Would you have a better approach to this scheme that you like to share?

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  • how to speed up the code??

    - by kaushik
    i have very huge code about 600 lines plus. cant post the whole thing here. but a particular code snippet is taking so much time,leading to problems. here i post that part of code please tell me what to do speed up the processing.. please suggest the part which may be the reason and measure to improve them if this small part of code is understandable. using_data={} def join_cost(a , b): global using_data #print a #print b save_a=[] save_b=[] print 1 #for i in range(len(m)): #if str(m[i][0])==str(a): save_a=database_index[a] #for i in range(len(m)): # if str(m[i][0])==str(b): #print 'save_a',save_a #print 'save_b',save_b print 2 save_b=database_index[b] using_data[save_a[0]]=save_a s=str(save_a[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') print 3 for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) end_time=save_a[4] #print end_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(end_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 q=[] print 4 l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') q=k3.split(' ') #print q print 5 s=str(save_b[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) strt_time=save_b[3] #print strt_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(strt_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 w=[] l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') w=k3.split(' ') #print w cost=0 for i in range(12): #print q[i] #print w[i] h=float(q[i])-float(w[i]) cost=cost+math.pow(h,2) j_cost=math.sqrt(cost) #print cost return j_cost def target_cost(a , b): a=(b+1)*3 b=(a+1)*2 t_cost=(a+b)*5/2 return t_cost r1='shht:ra_77' r2='grx_18' g=[] nodes=[] nodes=nodes+[[r1]] for i in range(len(y_in_db_format)): g=y_in_db_format[i] #print g #print g[0] g.remove(str(g[0])) nodes=nodes+[g] nodes=nodes+[[r2]] print nodes print "lenght of nodes",len(nodes) lists=[] #lists=lists+[r1] for i in range(len(nodes)): for j in range(len(nodes[i])): lists=lists+[nodes[i][j]] #lists=lists+[r2] print lists distance={} for i in range(len(lists)): if i==0: distance[str(lists[i])]=0 else: distance[str(lists[i])]=long(123231223) #print distance group_dist=[] infinity=long(123232323) for i in range(len(nodes)): distances=[] for j in range(len(nodes[i])): #distances=[] if i==0: distances=distances+[[nodes[i][j], 0]] else: distances=distances+[[nodes[i][j],infinity]] group_dist=group_dist+[distances] #print distances print "group_distances",group_dist #print "check",group_dist[0][0][1] #costs={} #for i in range(len(lists)): #if i==0: # costs[str(lists[i])]=1 #else: # costs[str(lists[i])]=get_selfcost(lists[i]) path=[] for i in range(len(nodes)): mini=[] if i!=(len(nodes)-1): #temp=long(123234324) #Now calculate the cost between the current node and each of its neighbour for k in range(len(nodes[(i+1)])): for j in range(len(nodes[i])): current=nodes[i][j] #print "current_node",current j_distance=join_cost( current , nodes[i+1][k]) #t_distance=target_cost( current , nodes[i+1][k]) t_distance=34 #print distance #print "distance between current and neighbours",distance total_distance=(.5*(float(group_dist[i][j][1])+float(j_distance))+.5*(float(t_distance))) #print "total distance between the intial_nodes and current neighbour",total_distance if int(group_dist[i+1][k][1]) > int(total_distance): group_dist[i+1][k][1]=total_distance #print "updated distance",group_dist[i+1][k][1] a=current #print "the neighbour",nodes[i+1][k],"updated the value",a mini=mini+[[str(nodes[i+1][k]),a]] print mini

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  • Data Structure for a particular problem??

    - by AGeek
    Hi, Which data structure can perform insertion, deletion and searching operation in O(1) time in the worst case. We may assume the set of elements are integers drawn from a finite set 1,2,...,n, and initialization can take O(n) time. I can only think of implementing a hash table. Implementing it with Trees will not give O(1) time complexity for any of the operation. Or is it possible?? Kindly share your views on this, or any other data structure apart from these.. Thanks..

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  • Why use hashing to create pathnames for large collections of files?

    - by Stephen
    Hi, I noticed a number of cases where an application or database stored collections of files/blobs using a has to determine the path and filename. I believe the intended outcome is a situation where the path never gets too deep, or the folders ever get too full - too many files (or folders) in a folder making for slower access. EDIT: Examples are often Digital libraries or repositories, though the simplest example I can think of (that can be installed in about 30s) is the Zotero document/citation database. Why do this? EDIT: thanks Mat for the answer - does this technique of using a hash to create a file path have a name? Is it a pattern? I'd like to read more, but have failed to find anything in the ACM Digital Library

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  • EC2 server in VPC stops responding after joining domain

    - by Geoff
    We have a EC2 Windows Server set up and running in our VPC, connected to our network via a Juniper 5GT. This is working well, with the tunnel up and stable. If I then join the server to our local domain, it appears to work - I can then log on using domain credentials, and use domain accounts when applying security to folders etc. After I log out, if I give it around an hour, the box becomes unresponsive. I can't ping it, although a tracert goes all the way barring the last hop - so the tunnel is ok. I can't RDP into it. If I reboot it, then it works for a while before doing the same thing. Un-joining it from the domain fixes the problem, and it stays up and stable. The event logs don't show anything obvious, at least to me. Any ideas?

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  • SHA-256 encryption wrong result in Android

    - by user642966
    I am trying to encrypt 12345 using 1111 as salt using SHA-256 encoding and the answer I get is: 010def5ed854d162aa19309479f3ca44dc7563232ff072d1c87bd85943d0e930 which is not same as the value returned by this site: http://hash.online-convert.com/sha256-generator Here's the code snippet: public String getHashValue(String entity, String salt){ byte[] hashValue = null; try { MessageDigest digest = MessageDigest.getInstance("SHA-256"); digest.update(entity.getBytes("UTF-8")); digest.update(salt.getBytes("UTF-8")); hashValue = digest.digest(); } catch (NoSuchAlgorithmException e) { Log.i(TAG, "Exception "+e.getMessage()); } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } return BasicUtil.byteArrayToHexString(hashValue); } I have verified my printing method with a sample from SO and result is fine. Can someone tell me what's wrong here? And just to clarify - when I encrypt same value & salt in iOS code, the returned value is same as the value given by the converting site.

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  • Does to_json require parameters? what about within rails?

    - by Harry Wood
    Does to_json require parameters? what about within rails? I started getting the error "wrong number of arguments (0 for 1)" when doing myhash.to_json Unfortunately I'm not sure when this error started happening, but I guess it relates to some versions of either rails or the json gem. I suppose my code (in a rails controller) is using the ActiveSupport::JSON version of to_json, rather than the to_josn method supported by the json gem. ActiveSupport::JSON vs JSON In environment.rb I have RAILS_GEM_VERSION = '2.3.2' and also config.gem "json", :version=> '1.1.7' It's just a simple hash structure containing primitives which I want to convert in my controller, and it was working, but now I can't seem to run to_json without passing parameters.

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  • Cross-Forest Trust

    - by cdalley
    I am looking at testing a cross-domain trust we can have two domain controllers (with different forests and domain names) setup so we can move everyone onto the new domain. We do NOT run exchange on site and we do not have any links to O365 to AD currently. Onto the problem: I have setup two DCs in a Virtual Machine: They are on the same network 192.168.0.* The Windows 2003 server: Name: OLDSRVR "Clone" of our current Domain Controller IP: 192.168.0.1 Domain: internal.test.com The Windows 2012 server: Name: ADCTEST01 Brand new domain setup from scratch separate to internal.test.com Domain: internal.test2.com IP: 192.168.0.2 OLDSRVR can only see ADCTEST if it has dynamic IP set. If I set a static IP it cannot see it. If I try using the dynamic IP and try to join it gets to the end then complains "??The trust relationship between this workstation and the primary domain failed" Any ideas?

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  • pipelined function

    - by user289429
    Can someone provide an example of how to use parallel table function in oracle pl/sql. We need to run massive queries for 15 years and combine the result. SELECT * FROM Table(TableFunction(cursor(SELECT * FROM year_table))) ...is what we want effectively. The innermost select will give all the years, and the table function will take each year and run massive query and returns a collection. The problem we have is that all years are being fed to one table function itself, we would rather prefer the table function being called in parallel for each of the year. We tried all sort of partitioning by hash and range and it didn't help. Also, can we drop the keyword PIPELINED from the function declaration? because we are not performing any transformation and just need the aggregate of the resultset.

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  • Accessing GMail "View as HTML" content programatically?

    - by Amethi
    I love the "View as HTML" option in GMail when viewing attachments. I would love to be able to use this feature programatically, i.e. check a GMail inbox, read emails, if there are attachments, get the html view and use that content. I'm looking to do this in C Sharp (on a Mac, can't find the hash symbol). Does anyone know if this is possible or if there's another solution to easily get content from a GMail account, regardless of what format it's in? I.E html, pdf, Word doc, etc. The GMail Inbox Feed api isn't good enough and before I start trying to build an IMAP solution that pulls in PDF/Word doc converters, I thought it'd be good to ask here.

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  • resizing arrays when close to memory capacity

    - by user548928
    So I am implementing my own hashtable in java, since the built in hashtable has ridiculous memory overhead per entry. I'm making an open-addressed table with a variant of quadratic hashing, which is backed internally by two arrays, one for keys and one for values. I don't have the ability to resize though. The obvious way to do it is to create larger arrays and then hash all of the (key, value) pairs into the new arrays from the old ones. This falls apart though when my old arrays take up over 50% of my current memory, since I can't fit both the old and new arrays in memory at the same time. Is there any way to resize my hashtable in this situation Edit: the info I got for current hashtable memory overheads is from here How much memory does a Hashtable use? Also, for my current application, my values are ints, so rather than store references to Integers, I have an array of ints as my values.

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  • How to make GhostScript PS2PDF stop subsetting fonts

    - by gavin-softyolk
    I am using the ps2pdf14 utility that ships with GhostScript, and I am having a problem with fonts. It does not seem to matter what instructions I pass to the command, it insists on subsetting any fonts it finds in the source document. e.g -dPDFSETTINGS#/prepress -dEmbedAllFonts#true -dSubsetFonts#false -dMaxSubsetPct#0 Note that the # is because the command is running on windows, it is the same as =. If anyone has any idea how to tell ps2pdf not to subset fonts, I would be very greatful. Thanks --------------------------Notes ------------------------------------------ The source file is a pdf containing embedded fonts, so it is the fonts already embedded in the source file, that I need to prevent being subset in the destination file. Currently all source file embedded fonts are subset, in some cases this is not apparent from the font name, i.e it contains no hash, and appears at first glance to be the full font, however the widths array has been subset in all cases.

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  • Best solution for language documentation.

    - by Simone Margaritelli
    I'm developing a new object oriented scripting language and the project itself is quite ready for audience now, so i'm starting to think about a serious (not as "drafty" as it is right now) way of document its grammar, functions from standard library and standard library classes. I've looked a bit around and almost every language hash its own web application for the documentation, Python uses Sphinx for instance. Which is the best PHP (don't have the time/will to install mod_who_knows_what on my server) application to accomplish this? I've used mediawiki a bit but i found its tag system a little bit hard to use in this context. Thanks for your answers.

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  • does a switch idiom make sense in this case?

    - by the ungoverned
    I'm writing a parser/handler for a network protocol; the protocol is predefined and I am writing an adapter, in python. In the process of decoding the incoming messages, I've been considering using the idiom I've seen suggested elsewhere for "switch" in python: use a hash table whose keys are the field you want to match on (a string in this case) and whose values are callable expressions: self.switchTab = { 'N': self.handleN, 'M': self.handleM, ... } Where self.handleN, etc., are methods on the current class. The actual switch looks like this: self.switchTab[selector]() According to some profiling I've done with cProfile (and Python 2.5.2) this is actually a little bit faster than a chain of if..elif... statements. My question is, do folks think this is a reasonable choice? I can't imagine that re-framing this in terms of objects and polymorphism would be as fast, and I think the code looks reasonably clear to a reader.

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  • How does this Perl grep work to determine the union of several hashes?

    - by titaniumdecoy
    I don't understand the last line of this function from Programming Perl 3e. Here's how you might write a function that does a kind of set intersection by returning a list of keys occurring in all the hashes passed to it: @common = inter( \%foo, \%bar, \%joe ); sub inter { my %seen; for my $href (@_) { while (my $k = each %$href) { $seen{$k}++; } } return grep { $seen{$_} == @_ } keys %seen; } I understand that %seen is a hash which maps each key to the number of times it was encountered in any of the hashes provided to the function.

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  • Killing the mysqld process

    - by Josh K
    I have a table with ~800k rows. I ran an update users set hash = SHA1(CONCAT({about eight fields})) where 1; Now I have a hung Sequel Pro process and I'm not sure about the mysqld process. This is two questions: What harm can possibly come from killing these programs? I'm working on a separate database, so no damage should come to other databases on the system, right? Assume you had to update a table like this. What would be a quicker / more reliable method of updating without writing a separate script. I just checked with phpMyAdmin and it appears as though the query is complete. I still have Sequel Pro using 100% of both my cores though...

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  • Where can I find a link to download the SP2 of OES2?

    - by Philippe
    Hi, I have a Netware Novell server with an eDirectory and different objects configured. I implemented an OEServer2 SP1 to emulate a DSfW to manage the eDirectory with AD. I join the domain with the Administrator login and I am logged as the Administrator domain. So far, there are no problems. When I open the MMC window on Windows Server 08 and snap in the "Active Directory Users and Computers" I can see all the OUs and objects presented in the Netware N. server. But, when I select some OUs I can have an error, and when I select other I don’t have this error. Error: “Data from XXXXX is not available from Domain Controller OES2.yyyy.local because: The server is unwilling to process the request. Try again later, or choose another DC by selecting Connect to Domain Controller on the Domain context menu.” With XXXX= OU’s name and yyyy.local= domain name and OES2 server name If somebody can upload this SP or post a link to download it... Thank you for your help!

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  • What's the best way to match a query to a set of keywords?

    - by Ryan Detzel
    Pretty much what you would assume Google does. Advertisers come in and big on keywords, lets say "ipod", "ipod nano", "ipod 60GB", "used ipod", etc. Then we have a query, "I want to buy an ipod nano" or "best place to buy used ipods" what kind of algorithms and systems are used to match those queries to the keyword set. I would imagine that some of those keyword sets are huge, 100k keywords made up of one or more actual words. on top of that queries can be 1-n words as well. Any thoughts, links to wikipedia I can start reading? From what I know already I would use some stemmed hash in disk(CDB?) and a bloom filter to check to see if I should even go to disk.

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  • How does Hibernate detect dirty state of an entity object?

    - by ???'Lenik
    Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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  • client subscribed to a multicast group not receiving data

    - by Abruzzo Forte e Gentile
    I have a network that was setup for multicast traffic IN Machine A there is a server application generating multi-cast traffic. I have also different clients subscribing to that mulicast traffic -some client are in the same machine A -other clients are in machine B,C,D # Address I am using IP : 239.193.0.21 PORT: 20401 I don't know why but the client in machine A , even if they join the group, don't receive any data while (and this is the funny part) machine B,C and D receive everything. Checking with Wirshark I can see that the UDP traffic flow is there in Machine A. I am using LInux/Red-Hat Enterprise 6.2 What should I look at? Any setting in the os? Firewall or what?

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  • How can i pass Twig sub parameter?

    - by aliocee
    hi, Help i cant pass my hash key to twig subroutine. here: foreach my $word (sort { $keywords{$a} <=> $keywords{$b} } keys (%keywords)) { my $t = XML::Twig->new( twig_roots => { 'Id' => \&insert($keywords{$word}) } ); $t->parse($docsums); sub insert { my($t, $id, $k)= @_; my $p = $id->text; my $query = "insert into pres (id, wid, p) values(DEFAULT, '$k', '$p')"; my $sql = $connect->prepare($query); $sql->execute( ); } } Thanks.

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  • How do I share a home printer under Windows if the computer is part of a domain?

    - by Sorin Sbarnea
    I do have my work laptop at home and I want to share an USB printer in order to be able to print to it from my MacBook. Currently Windows 7 is refusing to share the printer because the computer is part of a domain and it tells me that I need to join a homegroup in order to be able to do that. Also it tells me that he cannot create this homegroup and this group has to be create by another Windows 7 computer from my network. As you can imagine I do have only one Windows computer on my home network. How can I solve this problem?

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  • What's the best way of using a pair (triple, etc) of values as one value in C#?

    - by Yacoder
    That is, I'd like to have a tuple of values. The use case on my mind: Dictionary<Pair<string, int>, object> or Dictionary<Triple<string, int, int>, object> Are there built-in types like Pair or Triple? Or what's the best way of implementing it? Update There are some general-purpose tuples implementations described in the answers, but for tuples used as keys in dictionaries you should additionaly verify correct calculation of the hash code. Some more info on that in another question. Update 2 I guess it is also worth reminding, that when you use some value as a key in dictionary, it should be immutable.

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