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• What techniques can be used to detect so called "black holes" (a spider trap) when creating a web crawler?

  - by Tom

  When creating a web crawler, you have to design somekind of system that gathers links and add them to a queue. Some, if not most, of these links will be dynamic, which appear to be different, but do not add any value as they are specifically created to fool crawlers. An example: We tell our crawler to crawl the domain evil.com by entering an initial lookup URL. Lets assume we let it crawl the front page initially, evil.com/index The returned HTML will contain several "unique" links: evil.com/somePageOne evil.com/somePageTwo evil.com/somePageThree The crawler will add these to the buffer of uncrawled URLs. When somePageOne is being crawled, the crawler receives more URLs: evil.com/someSubPageOne evil.com/someSubPageTwo These appear to be unique, and so they are. They are unique in the sense that the returned content is different from previous pages and that the URL is new to the crawler, however it appears that this is only because the developer has made a "loop trap" or "black hole". The crawler will add this new sub page, and the sub page will have another sub page, which will also be added. This process can go on infinitely. The content of each page is unique, but totally useless (it is randomly generated text, or text pulled from a random source). Our crawler will keep finding new pages, which we actually are not interested in. These loop traps are very difficult to find, and if your crawler does not have anything to prevent them in place, it will get stuck on a certain domain for infinity. My question is, what techniques can be used to detect so called black holes? One of the most common answers I have heard is the introduction of a limit on the amount of pages to be crawled. However, I cannot see how this can be a reliable technique when you do not know what kind of site is to be crawled. A legit site, like Wikipedia, can have hundreds of thousands of pages. Such limit could return a false positive for these kind of sites. Any feedback is appreciated. Thanks.

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• injection attack (I thought I was protected!) <?php /**/eval(base64_decode( everywhere

  - by Cyprus106

  I've got a fully custom PHP site with a lot of database calls. I just got injection hacked. This little chunk of code below showed up in dozens of my PHP pages. <?php /**/ eval(base64_decode(big string of code.... I've been pretty careful about my SQL calls and such; they're all in this format: $query = sprintf("UPDATE Sales SET `Shipped`='1', `Tracking_Number`='%s' WHERE ID='%s' LIMIT 1 ;", mysql_real_escape_string($trackNo), mysql_real_escape_string($id)); $result = mysql_query($query); mysql_close(); For the record, I rarely use mysql_close() at the end though. That just happened to be the code I grabbed. I can't think of any places where I don't use mysql_real_escape_string(), (although I'm sure there's probably a couple. I'll be grepping soon to find out) There's also no places where users can put in custom HTML or anything. In fact, most of the user-accessible pages, if they use SQL calls at all, are almost inevitably "SELECT * FROM" pages that use a GET or POST, depending. Obviously I need to beef up my security, but I've never had an attack like this and I'm not positive what I should do. I've decided to put limits on all my inputs and go through looking to see if i missed a mysql_real_escape_string somewhere... Anybody else have any suggestions? Also... what does this type of code do? Why is it there?

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• Regular expressions - finding and comparing the first instance of a word

  - by Dan

  Hi there, I am currently trying to write a regular expression to pull links out of a page I have. The problem is the links need to be pulled out only if the links have 'stock' for example. This is an outline of what I have code wise: <td class="prd-details"> <a href="somepage"> ... <span class="collect unavailable"> </td> <td class="prd-details"> <a href="somepage"> ... <span class="collect available"> </td> What I would like to do is pull out the links only if 'collect available' is in the tag. I have tried to do this with the regular expression: (?s)prd-details[^=]+="([^"]+)" .+?collect{1}[^\s]+ available However on running it, it will find the first 'prd-details' class and keep going until it finds 'collect available', thereby taking the incorrect results. I thought by specifying the {1} after the word collect it would only use the first instance of the word it finds, but apparently I'm wrong. I've been trying to use different things such as positive and negative lookaheads but I cant seem to get anything to work. Might anyone be able to help me with this issue? Thanks, Dan

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• I am totally unable to add a fileTree (JQuery fileTree addon) to my asp.net page

  - by Gadgetsan

  okay, so i have an asp.net (C#) application and i want to add a list of file and folders on the page, so i figured i should use JQuery fileTree (http://abeautifulsite.net/2008/03/jquery-file-tree/#download) but now i am totally unable to display the file list. I initialise the page this way: Site.Master: <link rel="stylesheet" type="text/css" href="../../Content/superfish.css" media="screen"> <link href="../../Content/jqueryFileTree.css" rel="stylesheet" type="text/css" /> <script src="../../Scripts/jquery-1.4.1.min.js" type="text/javascript"></script> <script src="../../Scripts/jquery.easing.1.3.js" type="text/javascript"></script> <script src="../../Scripts/jqueryFileTree.js" type="text/javascript"></script> <script src="../../Scripts/JqueryUI/js/jquery-ui-1.8.1.custom.min.js" type="text/javascript"></script> <script type="text/javascript" src="../../Scripts/jquery.dataTables.js"></script> <script type="text/javascript" src="../../Scripts/superfish.js"></script> <script type="text/javascript"> $(document).ready(function() { test = $('#fileTree').fileTree({script: "jqueryFileTree.aspx" }, function(file) { openFile(file); }); $("button").button(); oTable = $('#data').dataTable({ "bJQueryUI": true, "sPaginationType": "full_numbers", "bSort": true }); }); </script> and in the page, i put my div this way: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> Documents but i'm positive that jqueryFileTree.aspx is never "called" because if i return this page in my controller, it shows the list of files/folder correctly, so it's also not a problem with my aspx connector... Also i checked, on the JS console, it gives no error and there is nothing more in the page source code i've been trying to solve this all day without success so your help is apreciated

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• problem with fork()

  - by john

  I'm writing a shell which forks, with the parent reading the input and the child process parsing and executing it with execvp. pseudocode of main method: do{ pid = fork(); print pid; if (p<0) { error; exit; } if (p>0) { wait for child to finish; read input; } else { call function to parse input; exit; } }while condition return; what happens is that i never seem to enter the child process (pid printed is always positive, i never enter the else). however, if i don't call the parse function and just have else exit, i do correctly enter parent and child alternatingly. full code: int main(int argc, char *argv[]){ char input[500]; pid_t p; int firstrun = 1; do{ p = fork(); printf("PID: %d", p); if (p < 0) {printf("Error forking"); exit(-1);} if (p > 0){ wait(NULL); firstrun = 0; printf("\n> "); bzero(input, 500); fflush(stdout); read(0, input, 499); input[strlen(input)-1] = '\0'; } else exit(0); else { if (parse(input) != 0 && firstrun != 1) { printf("Error parsing"); exit(-1); } exit(0); } }while(strcmp(input, "exit") != 0); return 0; }

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• ASP MVC - Routing Required?

  - by evo_9

  I've been reading up on MVC2 which came in VS2010 and it sounds pretty interesting. I'm actually in the middle of a large multi-tenant application project, and have just started coding the UI. I'm considering changing to MVC as I'm not that far along at this point. I have some questions about the Routing capabilities, namely are they required to use MVC or can I more or less ignore Routing? Or do I have to setup a default routing record that will make things work like standard ASPX (as far as routing alone is concerned)? The reason why I don't want to use Routing is because I've already defined a custom URL 'rewrite' mechanism of my own (which fires on session_start). In addition, I'm using jquery and opens-standards for the entire UI, and MVC's aspx overhead-free approach seems like a better fit based on how I've already started to build the application (I am not using viewstate at all, for example). I guess my big concern is whether the routing can be ignored, of if I will have to re-implement my custom URL rewriting to work with MVC, and if that's the case, how would I do that? As a new Routing routine, or stick with the session_start (if that's even possible?). Lastly, I don't want to use anything even remotely 'intelligent/readable' for the url - for a site like StackOverflow, the readability of the URL is a positive, but the opposite is true if it's not a public website like this one. In fact, it would seem to me that the more friendly MVC routing URL (which indirectly show method names) could pose a security risk on a private, non-public website app like I'm developing. For all these reasons I would love to use the lightweight aspects of MVC but skip the Routing entirely - is this possible?

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• JQuery Dragging Outside Parent

  - by Andy

  I'm using JQuery's draggable(); to make li elements draggable. The only problem is when the element is dragged outside its parent, it doesn't show up. That is, it doesn't leave the confines of its parent div. An example is here: http://imgur.com/N2N1L.png - it's as if the z-index for everything else has greater priority (and the element slides under everything). Here's the code: $('.photoList li').draggable({ distance: 20, snap: theVoteBar, revert: true, containment: 'document' }); And the li elements are placed in DIVs like this: <div class="coda-slider preload" id="coda-slider-1"> <div class="panel"> <div class="panel-wrapper"> <h2 class="title" style="display:none;">Page 1</h2> <ul class="photoList"> <li> <img class="ui-widget-content" src="photos/1.jpg" style="width:100px;height:100px;" /> </li> </ul> </div> </div> I'm positive the problem is it won't leave its parent container, but I'm not sure what to do to get it out. Any direction or help would be appreciated GREATLY!

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• How to handle management trying to interfere with the project (including architecture decision)

  - by Zwei Steinen

  I feel this is not a very good question to post on SO, but I need some advice from experienced developers... (I'm a second year developer) I guess this is a problem to many, many projects, but in our case, it is getting intense. There were so much interference from people that don't know a bit about software development, that our development came to an almost complete stop. We had to literary escape to another location to get any useful job done. Now we were happily producing results, but then I get a request for a "meeting" and it's them again. I have a friendly relationship with them, but I feel very daunted at the thought of talking about non-sense all over again. Should I be firm and tell them to shut up and wait for our results? Or should I be diplomatic and create an illusion they are making a positive contribution or something?? My current urge is to be unfriendly and murmur some stuff so they will give up or something. What would you do if you were in this situation?

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• how to Compute the average probe length for success and failure - Linear probe (Hash Tables)

  - by fang_dejavu

  hi everyone, I'm doing an assignment for my Data Structures class. we were asked to to study linear probing with load factors of .1, .2 , .3, ...., and .9. The formula for testing is: The average probe length using linear probing is roughly Success-- ( 1 + 1/(1-L)**2)/2 or Failure-- (1+1(1-L))/2. we are required to find the theoretical using the formula above which I did(just plug the load factor in the formula), then we have to calculate the empirical (which I not quite sure how to do). here is the rest of the requirements **For each load factor, 10,000 randomly generated positive ints between 1 and 50000 (inclusive) will be inserted into a table of the "right" size, where "right" is strictly based upon the load factor you are testing. Repeats are allowed. Be sure that your formula for randomly generated ints is correct. There is a class called Random in java.util. USE it! After a table of the right (based upon L) size is loaded with 10,000 ints, do 100 searches of newly generated random ints from the range of 1 to 50000. Compute the average probe length for each of the two formulas and indicate the denominators used in each calculationSo, for example, each test for a .5 load would have a table of size approximately 20,000 (adjusted to be prime) and similarly each test for a .9 load would have a table of approximate size 10,000/.9 (again adjusted to be prime). The program should run displaying the various load factors tested, the average probe for each search (the two denominators used to compute the averages will add to 100), and the theoretical answers using the formula above. .** how do I calculate the empirical success?

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• Find min. "join" operations for sequence

  - by utyle

  Let's say, we have a list/an array of positive integers x1, x2, ... , xn. We can do a join operation on this sequence, that means that we can replace two elements that are next to each other with one element, which is sum of these elements. For example: - array/list: [1;2;3;4;5;6] we can join 2 and 3, and replace them with 5; we can join 5 and 6, and replace them with 11; we cannot join 2 and 4; we cannot join 1 and 3 etc. Main problem is to find minimum join operations for given sequence, after which this sequence will be sorted in increasing order. Note: empty and one-element sequences are sorted in increasing order. Basic examples: for [4; 6; 5; 3; 9] solution is 1 (we join 5 and 3) for [1; 3; 6; 5] solution is also 1 (we join 6 and 5) What I am looking for, is an algorithm that solve this problem. It could be in pseudocode, C, C++, PHP, OCaml or similar (I mean: I woluld understand solution, if You wrote solution in one of these languages). I would appreciate Your help.

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• FTPing a file to Mainframe using Java, Apache Common Net

  - by SKR

  I'm am trying to upload a file into mainframe server using FTP. My code is below FTPClient client = new FTPClient(); InputStream in = null; FileInputStream fis = null; try{ client.connect("10.10.23.23"); client.login("user1", "pass123"); client.setFileType(FTPClient.BINARY_FILE_TYPE); int reply ; reply = client.getReplyCode(); System.out.println("Reply Code:"+reply); if(FTPReply.isPositiveCompletion(reply)){ System.out.println("Positive reply"); String filename ="D:\\FILE.txt"; in = new FileInputStream(filename); client.storeFile("FILE.TXT", in); client.logout(); fis.close(); }else{ System.out.println("Negative reply"); } }catch(final Throwable t){ t.printStackTrace(); } The code gets struck in client.storeFile("FILE.TXT", in); I am unable to debug. Please suggest ways / solutions.

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• Is WordPress MVC compliant?

  - by kovshenin

  Some people consider WordPress a blogging platform, some think of it as a CMS, some refer to WordPress as a development framework. Whichever it is, the question still remains. Is WordPress MVC compliant? I've read the forums and somebody asked about MVC about three years ago. There were some positive answers, and some negative ones. While nobody knows exactly what MVC is and everybody thinks of it in their own way, there's still a general concept that's present in all the discussions. I have little experience with MVC frameworks and there doesn't seem to be anything about the framework itself. Most of the MVC is done by the programmer, am I right? Now, going back to WordPress, could we consider the core rewrite engine (WP_Rewrite) the controller? Queries & plugin logic as the model? And themes as the view? Or am I getting it all wrong? Thanks ;)

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• C/C++: feedback in analyzing a code example

  - by KaiserJohaan

  Hello, I have a piece of code from an assignment I am uncertain about. I feel confident that I know the answer, but I just want to double-check with the community incase there's something I forgot. The title is basically secure coding and the question is just to explain the results. int main() { unsigned int i = 1; unsigned int c = 1; while (i > 0) { i = i*2; c++; } printf("%d\n", c); return 0; } My reasoning is this: At first glance you could imagine the code would run forever, considering it's initialized to a positive value and ever increasing. This of course is wrong because eventually the value will grow so large it will cause an integer overflow. This in turn is not entirely true either, because eventally it will force the variable 'i' to be signed by making the last bit to 1 and therefore regarded as a negative number, therefore terminating the loop. So it is not writing to unallocated memory and therefore cause integer overflow, but rather violating the data type and therefore causing the loop to terminate. I am quite sure this is the reason, but I just want to double check. Any opinions?

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• Serialized NHibernate Configuration objects - detect out of date or rebuild on demand?

  - by fostandy

  I've been using serialized nhibernate configuration objects (also discussed here and here) to speed up my application startup from about 8s to 1s. I also use fluent-nhibernate, so the path is more like ClassMap class definitions in code fluentconfiguration xml nhibernate configuration configuration serialized to disk. The problem from doing this is that one runs the risk of out of date mappings - if I change the mappings but forget to rebuild the serialized configuration, then I end up using the old mappings without realising it. This does not always result in an immediate and obvious error during testing, and several times the misbehaviour has been a real pain to detect and fix. Does anybody have any idea how I would be able to detect if my classmaps have changed, so that I could either issue an immediate warning/error or rebuild it on demand? At the moment I am comparing timestamps on my compiled assembly against the serialized configuration. This will pickup mapping changes, but unfortunately it generates a massive false positive rate as ANY change to the code results in an out of date flag. I can't move the classmaps to another assembly as they are tightly integrated into the business logic. This has been niggling me for a while so I was wondering if anybody had any suggestions?

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• output not updating until next clock cycle

  - by EquinoX

  I have the code module below always @(posedge Clk) begin ForwardA = 0; ForwardB = 0; //EX Hazard if (EXMEMRegWrite == 1) begin if (EXMEMrd != 0) if (EXMEMrd == IDEXrs) ForwardA = 2'b10; if (EXMEMrd == IDEXrt && IDEXTest == 0) ForwardB = 2'b10; end //MEM Hazard if (MEMWBRegWrite == 1) begin if (MEMWBrd != 0) begin if (!(EXMEMRegWrite == 1 && EXMEMrd != 0 && (EXMEMrd == IDEXrs))) if (MEMWBrd == IDEXrs) ForwardA = 2'b01; if (IDEXTest == 0) begin if (!(EXMEMRegWrite == 1 && EXMEMrd != 0 && (EXMEMrd == IDEXrt))) if (MEMWBrd == IDEXrt) ForwardB = 2'b01; end end end end The problem is that the output, which is ForwardA and ForwardB is not updated not on the rising clock edge rather than on the next rising clock edge... why is this?? How do I resolve so that the output is updated on the same positive rising clock edge? Here's what I mean: ForwardA is updated with 2 on the next rising clock edge and not on the same rising clock edge

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• Break a while loop without using If or Break

  - by Justin

  I need to create a program that uses while to find the volume of a cylinder. I need the while loop to break if the user inputs a negative value for the height. My code looks like this: double sentinel=1, h=1, v=0, r, count=0; // declares all variables needed final double PI=3.14159; boolean NotNegative=true; while(NotNegative){// && count==0){ // while both the height is positive AND the total times run is 0 System.out.print("Enter height (Use negative to exit): "); // has the user input the height h=Double.parseDouble(br.readLine()); sentinel=h; // save sentinel as the inputted height while(sentinel>0){ System.out.print("Enter radius: "); // have the user input the radius r=Double.parseDouble(br.readLine()); v=PI*(r*r)*h; // find the volume System.out.println("The volume is " + v); // print out the volume count++; // increase the count each time this runs NotNegative=true; sentinel=-1; } } Any help?

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• Regex to check if exact string exists

  - by Jayrox

  I am looking for a way to check if an exact string match exists in another string using Regex or any better method suggested. I understand that you tell regex to match a space or any other non-word character at the beginning or end of a string. However, I don't know exactly how to set it up. Search String: t String 1: Hello World, Nice to see you! t String 2: Hello World, Nice to see you! String 3: T Hello World, Nice to see you! I would like to use the search string and compare it to String 1, String 2 and String 3 and only get a positive match from String 1 and String 3 but not from String 2. Requirements: Search String may be at any character position in the Subject. There may or may not be a white-space character before or after it. I do not want it to match if it is part of another string; such as part of a word. For the sake of this question: I think I would do this using this pattern: /\bt\b/gi /\b{$search_string}\b/gi Does this look right? Can it be made better? Any situations where this pattern wouldn't work? Additional info: this will be used in PHP 5

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• Division by zero: Undefined Behavior or Implementation Defined in C and/or C++ ?

  - by SiegeX

  Regarding division by zero, the standards say: C99 6.5.5p5 - The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. C++03 5.6.4 - The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined. If we were to take the above paragraphs at face value, the answer is clearly Undefined Behavior for both languages. However, if we look further down in the C99 standard we see the following paragraph which appears to be contradictory(1): C99 7.12p4 - The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; Do the standards have some sort of golden rule where Undefined Behavior cannot be superseded by a (potentially) contradictory statement? Barring that, I don't think it's unreasonable to conclude that if your implementation defines the INFINITY macro, division by zero is defined to be such. However, if your implementation does not define such a macro, the behavior is Undefined. I'm curious what the consensus on this matter for each of the two languages. Would the answer change if we are talking about integer division int i = 1 / 0 versus floating point division float i = 1.0 / 0.0 ? Note (1) The C++03 standard talks about the library which includes the INFINITY macro.

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• SQL Server 2008 spatial index and CPU utilization with MapGuide Open Source 2.1

  - by Antonio de la Peña

  I have a SQL Server table with hundreds of thousands of geometry type parcels. I have made indexes on them trying different combinations of density and objects per cell settings. So far I'm settiling for LOW, LOW, MEDIUM, MEDIUM and 16 objects per cell and I made a SP that sets the bounding box according to the extents of the entities in the table. There is an incredible performance boost from queries taking almost minutes without index to less than seconds, it gets faster when the zoom is closer thus less objects are displayed. Yet the CPU utilization gets to 100% when querying for features, even when the queries themselves are fast. I'm worrying this will not fly in a production environment. I am using MapGuide Open Source 2.1 for this project, but I am positive the CPU load is caused by SQL Server. I wonder if my indexes are set properly. I haven't found any clear documentation on how to properly set them up. Every article I've read basically says "it depends..." but nothing specific. Do you have any recommendations for me, including books, articles? Thank you.

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• Shortest acyclic path on directed cyclic graph with negative weights/cycles

  - by Janathan

  I have a directed graph which has cycles. All edges are weighted, and the weights can be negative. There can be negative cycles. I want to find a path from s to t, which minimizes the total weight on the path. Sure, it can go to negative infinity when negative cycles exist. But what if I disallow cycles in the path (not in the original graph)? That is, once the path leaves a node, it can not enter the node again. This surely avoids the negative infinity problem, but surprisingly no known algorithm is found by a search on Google. The closest is Floyd–Warshall algorithm, but it does not allow negative cycles. Thanks a lot in advance. Edit: I may have generalized my original problem too much. Indeed, I am given a cyclic directed graph with nonnegative edge weights. But in addition, each node has a positive reward too. I want to find a simple path which minimizes (sum of edge weights on the path) - (sum of node rewards covered by the path). This can be surely converted to the question that I posted, but some structure is lost. And some hint from submodular analysis suggests this motivating problem is not NP-hard. Thanks a lot

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• Simple encryption - Sum of Hashes in C

  - by Dogbert

  I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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• Detection of negative integers using bit operations

  - by Nawaz

  One approach to check if a given integer is negative or not, could be this: (using bit operations) int num_bits = sizeof(int) * 8; //assuming 8 bits per byte! int sign_bit = given_int & (1 << (num_bits-1)); //sign_bit is either 1 or 0 if ( sign_bit ) { cout << "given integer is negative"<<endl; } else { cout << "given integer is positive"<<endl; } The problem with this solution is that number of bits per byte couldn't be 8, it could be 9,10, 11 even 16 or 40 bits per byte. Byte doesn't necessarily mean 8 bits! Anyway, this problem can be easily fixed by writing, //CHAR_BIT is defined in limits.h int num_bits = sizeof(int) * CHAR_BIT; //no assumption. It seems fine now. But is it really? Is this Standard conformant? What if the negative integer is not represented as 2's complement? What if it's representation in a binary numeration system that doesn't necessitate only negative integers to have 1 in it's most significant bit? Can we write such code that will be both portable and standard conformant? Related topics: Size of Primitive data types Why is a boolean 1 byte and not 1 bit of size?

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• Checking if radio buttons are checked in Firefox

  - by Andrew Song

  On my site, I have two checkboxes created in my ASP.NET MVC view like so: Html.RadioButton("check", "true", "true" == (string) ViewData["someKey"], new { id = "check1"}); Html.RadioButton("check", "false", "false" == (string) ViewData["someKey"], new { id = "check2"}); I am positive that ViewData["someKey"] has the value "true" in it. In my JS init function, I perform the following check: alert($('#check1').is(':checked') + " " + $('#check2').is(':checked')); In Firefox (and only Firefox), my alert dialog will show the following (it works as expected in every other browser): Initial page load: true false Normal refresh via Ctrl + R: false false Refresh skipping cache via Ctrl + Shift + R: true false I have tried many different methods of looking at the checkbox value, including $('#check1').attr('checked') without success. If I examine the HTML in Firebug, I can see that the first radio button has the property checked="checked" in it. Why is the checkbox value changing in FF when I refresh, and how can I mitigate this? Since this seems to be a FF-only bug, how can I change my code to make it work? This SO question seemed to ask something similar, but none of the proposed solutions seem to work in this case. Edit: I should also point out that when the radio button is rendered after the refresh in FF, it's not actually being displayed as checked either, despite what the HTML is telling me. Edit2: Adding raw HTML as per request <input id="check1" type="radio" value="True" name="check" checked="checked"/> <input id="check2" type="radio" value="False" name="check"/>

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• NSArray containObjects method

  - by Anthony Chan

  Hi, I have a simple question regarding xcode coding but don't know why things are not performing as I think. I have an array of objects (custom objects). I just want to check if this one is within the array. I used the following code: NSArray *collection = [[NSArray alloc] initWithObjects:A, B, C, nil]; //custom "Item" objects Item *tempItem = [[Fruit alloc] initWithLength:1 width:2 height:3]; //3 instance variables in "Item" objects if([collection containsObject:tempItem]) { NSLog(@"collection contains this item"); } I suppose the above checking will give me a positive result but it's not. Further, I checked whether the objects created are the same. NSLog(@"L:%i W:%i H:%i", itemToCheck.length, itemToCheck.width, itemToCheck.height); for (int i = 0, i < [collection count], i++) { Item *itemInArray = [collection objectAtIndex:i]; NSLog(@"collection contains L:%i W:%i H:%i", itemInArray.length, itemInArray.width, itemInArrayheight); } In the console, this is what I got: L:1 W:2 H:3 collection contains L:0 W:0 H:0 collection contains L:1 W:2 H:3 collection contains L:6 W:8 H:2 Obviously the tempItem is inside the collection array but nothing shows up when I use containsObject: to check it. Could anyone give me some direction which part I am wrong? Thanks a lot!

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• minimum L sum in a mxn matrix - 2

  - by hilal

  Here is my first question about maximum L sum and here is different and hard version of it. Problem : Given a mxn *positive* integer matrix find the minimum L sum from 0th row to the m'th row . L(4 item) likes chess horse move Example : M = 3x3 0 1 2 1 3 2 4 2 1 Possible L moves are : (0 1 2 2), (0 1 3 2) (0 1 4 2) We should go from 0th row to the 3th row with minimum sum I solved this with dynamic-programming and here is my algorithm : 1. Take a mxn another Minimum L Moves Sum array and copy the first row of main matrix. I call it (MLMS) 2. start from first cell and look the up L moves and calculate it 3. insert it in MLMS if it is less than exists value 4. Do step 2. until m'th row 5. Choose the minimum sum in the m'th row Let me explain on my example step by step: M[ 0 ][ 0 ] sum(L1 = (0, 1, 2, 2)) = 5 ; sum(L2 = (0,1,3,2)) = 6; so MLMS[ 0 ][ 1 ] = 6 sum(L3 = (0, 1, 3, 2)) = 6 ; sum(L4 = (0,1,4,2)) = 7; so MLMS[ 2 ][ 1 ] = 6 M[ 0 ][ 1 ] sum(L5 = (1, 0, 1, 4)) = 6; sum(L6 = (1,3,2,4)) = 10; so MLMS[ 2 ][ 2 ] = 6 ... the last MSLS is : 0 1 2 4 3 6 6 6 6 Which means 6 is the minimum L sum that can be reach from 0 to the m. I think it is O(8*(m-1)*n) = O(m*n). Is there any optimal solution or dynamic-programming algorithms fit this problem? Thanks, sorry for long question

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