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  • What would be the time complexity of counting the number of all structurally different binary trees?

    - by ktslwy
    Using the method presented here: http://cslibrary.stanford.edu/110/BinaryTrees.html#java 12. countTrees() Solution (Java) /** For the key values 1...numKeys, how many structurally unique binary search trees are possible that store those keys? Strategy: consider that each value could be the root. Recursively find the size of the left and right subtrees. */ public static int countTrees(int numKeys) { if (numKeys <=1) { return(1); } else { // there will be one value at the root, with whatever remains // on the left and right each forming their own subtrees. // Iterate through all the values that could be the root... int sum = 0; int left, right, root; for (root=1; root<=numKeys; root++) { left = countTrees(root-1); right = countTrees(numKeys - root); // number of possible trees with this root == left*right sum += left*right; } return(sum); } } I have a sense that it might be n(n-1)(n-2)...1, i.e. n!

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  • List<T> and IEnumerable difference

    - by Jonas Elfström
    While implementing this generic merge sort, as a kind of Code Kata, I stumbled on a difference between IEnumerable and List that I need help to figure out. Here's the MergeSort public class MergeSort<T> { public IEnumerable<T> Sort(IEnumerable<T> arr) { if (arr.Count() <= 1) return arr; int middle = arr.Count() / 2; var left = arr.Take(middle).ToList(); var right = arr.Skip(middle).ToList(); return Merge(Sort(left), Sort(right)); } private static IEnumerable<T> Merge(IEnumerable<T> left, IEnumerable<T> right) { var arrSorted = new List<T>(); while (left.Count() > 0 && right.Count() > 0) { if (Comparer<T>.Default.Compare(left.First(), right.First()) < 0) { arrSorted.Add(left.First()); left=left.Skip(1); } else { arrSorted.Add(right.First()); right=right.Skip(1); } } return arrSorted.Concat(left).Concat(right); } } If I remove the .ToList() on the left and right variables it fails to sort correctly. Do you see why? Example var ints = new List<int> { 5, 8, 2, 1, 7 }; var mergeSortInt = new MergeSort<int>(); var sortedInts = mergeSortInt.Sort(ints); With .ToList() [0]: 1 [1]: 2 [2]: 5 [3]: 7 [4]: 8 Without .ToList() [0]: 1 [1]: 2 [2]: 5 [3]: 7 [4]: 2 Edit It was my stupid test that got me. I tested it like this: var sortedInts = mergeSortInt.Sort(ints); ints.Sort(); if (Enumerable.SequenceEqual(ints, sortedInts)) Console.WriteLine("ints sorts ok"); just changing the first row to var sortedInts = mergeSortInt.Sort(ints).ToList(); removes the problem (and the lazy evaluation). EDIT 2010-12-29 I thought I would figure out just how the lazy evaluation messes things up here but I just don't get it. Remove the .ToList() in the Sort method above like this var left = arr.Take(middle); var right = arr.Skip(middle); then try this var ints = new List<int> { 5, 8, 2 }; var mergeSortInt = new MergeSort<int>(); var sortedInts = mergeSortInt.Sort(ints); ints.Sort(); if (Enumerable.SequenceEqual(ints, sortedInts)) Console.WriteLine("ints sorts ok"); When debugging You can see that before ints.Sort() a sortedInts.ToList() returns [0]: 2 [1]: 5 [2]: 8 but after ints.Sort() it returns [0]: 2 [1]: 5 [2]: 5 What is really happening here?

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  • How can I sort an NSTableColumn of NSStrings ignoring "The " and "A "?

    - by David Barry
    I've got a simple Core Data application that I'm working on to display my movie collection. I'm using an NSTableView, with it's columns bound to attributes of my Core Data store through an NSArrayController object. At this point the columns sort fine(for numeric values) when the column headers are clicked on. The issue I'm having is with the String sorting, they sort, however it's done in standard string fashion, with Uppercase letters preceding lowercase(i.e. Z before a). In addition to getting the case sorting to work properly, I would like to be able to ignore a prefix of "The " or "A " when sorting the strings. What is the best way to go about this in Objective-C/Cocoa?

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  • Node.js mongoose: how to use the .in and .sort methods of a query?

    - by Chris
    Hi there, I'm trying to wrap my head around mongoose, but I'm having a hard time finding any kind of documentation for some of the more advanced query options, specifically the .in and .sort methods. What's the syntax for sorting, for example, a Person by age? db.model("Person").find().sort(???).all(function(people) { }); Then, let's say I want to find a Movie based on a genre, where a Movie can have many genres (in this case, an array of strings). Presumably, I'd use the .in function to accomplish that, but I'm not sure what the syntax would be. Or perhaps I don't have to use the .in method at all...? Either way, I'm lost. db.model("Movie").find().in(???).all(function(movies) { }); Anyone have any ideas? Or even better, a link to some comprehensive documentation? Thanks! Chris

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  • I need a groovy criteria to get all the elements after i make sort on nullable inner object

    - by user1773876
    I have two domain classes named IpPatient,Ward as shown below. class IpPatient { String ipRegNo Ward ward static constraints = { ward nullable:true ipRegNo nullable:false } } class Ward { String name; static constraints = { name nullable:true } } now i would like to create criteria like def criteria=IpPatient.createCriteria() return criteria.list(max:max , offset:offset) { order("ward.name","asc") createAlias('ward', 'ward', CriteriaSpecification.LEFT_JOIN) } At present IpPatient table has 13 records, where 8 records of IpPatient doesn't have ward because ward can be null. when i sort with wardName i am getting 5 records those contain ward. I need a criteria to get all the elements after i make sort on nullable inner object.

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  • Does Ubuntu Server have any sort of cron job to automatically clear /tmp?

    - by DWilliams
    I know it clears out /tmp on reboots, but I haven't been able to find any sort of cron job on my server that clears /tmp. I recently set up a script that writes lots of files to /tmp and my server usually goes several months between reboots so I'm concerned about it being cluttered. I've seen several other distros that have a tmpwatch script installed by default. Ubuntu's repository seems to have replaced tmpwatch with tmpreaper. Is there any mechanism in place on Ubuntu (8.04 currently, soon to be upgraded to 10.04 when I get around to it) to clean up temp files on a server that doesn't regularly reboot or do I need to install tmpreaper?

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  • So does Apple recommend to not use predicates and sort descriptors in an NSFetchRequest?

    - by dontWatchMyProfile
    From the docs: To summarize, though, if you execute a fetch directly, you should typically not add Objective-C-based predicates or sort descriptors to the fetch request. Instead you should apply these to the results of the fetch. If you use an array controller, you may need to subclass NSArrayController so you can have it not pass the sort descriptors to the persistent store and instead do the sorting after your data has been fetched. I don't get it. What's wrong with using them on fetch requests? Isn't it stupid to get back a whole big bunch of managed objects just to pick out a 1% of them in memory, leaving 99% garbage floating around? Isn't it much better to only fetch from the persistent store what you really need, in the order you need it? Probably I did get that wrong...

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  • What causes a WPF ListCollectionView that uses custom sorting to re-sort its items?

    - by Drew Noakes
    Consider this code (type names genericised for the purposes of example): // Bound to ListBox.ItemsSource _items = new ObservableCollection<Item>(); // ...Items are added here ... // Specify custom IComparer for this collection view _itemsView = CollectionViewSource.GetDefaultView(_items) ((ListCollectionView)_itemsView).CustomSort = new ItemComparer(); When I set CustomSort, the collection is sorted as I expect. However I require the data to re-sort itself at runtime in response to the changing of the properties on Item. The Item class derives from INotifyPropertyChanged and I know that the property fires correctly as my data template updates the values on screen, only the sorting logic is not being called. I have also tried raising INotifyPropertyChanged.PropertyChanged passing an empty string, to see if a generic notification would cause the sorting to be initiated. No bananas. EDIT In response to Kent's suggestion I thought I'd point out that sorting the items using this has the same result, namely that the collection sorts once but does not re-sort as the data changes: _itemsView.SortDescriptions.Add( new SortDescription("PropertyName", ListSortDirection.Ascending));

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  • Is there a way to sort my windows within a screen session?

    - by jv1975
    I use screen and have ssh sessions open to a number of different machines from within my screen session. I'd like to keep them in order, for obvious reasons. Often I'll have to connect to a new machine which alphabetically/numerically should fit in between two existing windows. I can't find any way to reorder the windows other than with the "number" command, which swaps my current window with that at the number I specified. So adding a new window to the 15 I already have and then sticking it at position 2, while keeping all the other windows in order as well is cumbersome, to say the least, requiring swaps for all windows past #2. Is there anyway to sort the windows alphabetically? Or a way to "shift" all windows after a certain point up one spot? Or any other suggestions to insert a new window at an arbitrary point while still maintaining the order of all other windows? Thanks!

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  • Sort/Enumerate an NSArray from somewhere in the middle?

    - by Kenny Winker
    I have an NSArray, with objects ordered like so: a b c d e f I would like to enumerate through this array in this order: c d e f a b i.e. starting at some point that is not the beginning, but hitting all the items. I imagine this is a matter of sorting first and then enumerating the array, but I'm not sure if that's the best technique... or, frankly, how to sort the array like this. Edit Adding details: These will be relatively small arrays, varying from 3 to 10 objects. No concurrent access. I'd like to permanently alter the sort order of the array each time I do this operation.

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  • Java: Selected rows's index does not changes when I sort them!

    - by adrian7
    Hello, I have a Jtable on which I called the method table1.setAutoCreateRowSorter(true);. So this works on well. But I also have a methos in my JFrame class which is fired when i push a button. It gets the selected rows indexes using this code int selectedRows[] = this.table1.getSelectedRows();. And displays an edit window for the first row corresponding in the selected interval. The problem is that if I don't click on column's headers (I mean i don't sorte them at all) my method works perfect. But when I sort the row, the indexes of the rows doesn't seems to change at all - thus resulting an edit window for the old row whicn was initially in that position before making any sort. I am using JDK 6 could anyonw give ma a tip?

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  • Are memory barriers necessary for atomic reference counting shared immutable data?

    - by Dietrich Epp
    I have some immutable data structures that I would like to manage using reference counts, sharing them across threads on an SMP system. Here's what the release code looks like: void avocado_release(struct avocado *p) { if (atomic_dec(p->refcount) == 0) { free(p->pit); free(p->juicy_innards); free(p); } } Does atomic_dec need a memory barrier in it? If so, what kind of memory barrier? Additional notes: The application must run on PowerPC and x86, so any processor-specific information is welcomed. I already know about the GCC atomic builtins. As for immutability, the refcount is the only field that changes over the duration of the object.

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  • ASP.NET ObjectDataSource Sorting Twice

    - by user204588
    Hello, I'm working with some existing code uses an objectDataSource and that calls a sort method inside a DLL that I don't have access to. I'm trying to add a custom field to sort and I basically want to re-sort after the initial sort. I don't know if this can be done but before the GridView is displayed, I need to intercept the code and sort the way I want to sort. Any ideas? I'm lost.

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  • Jquery counting elements by class what is the best way to implement this?

    - by 133794m3r
    Ok what i'm trying to do is to count all of the elements in the current page with the same class and then i'm going to use it to be added onto a name for a input form. Basically i'm allowing users to click on an and then by doing so add another one for more of the same type of items. But i can't think of a way to count all of these simply with jquery/javascript. I was going to then name the item as something like name="whatever(total+1)", if anyone has a simple way to do this i'd be extremely grateful as javascript isn't exactly my native tongue and stack overflow usually has a ton of great answers and a great community so i'm hoping my query will not go unheard.

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  • im counting the number of characters in a file but i want to count the number of words that are less

    - by user320950
    i want to do this: reads the words in the file one at a time. (Use a string to do this) Counts three things: how many single-character words are in the file, how many short (2 to 5 characters) words are in the file, and how many long (6 or more characters) words are in the file. HELP HERE im not sure on how about reading file into a string. i know i have to something like this but i dont understand the rest. HELP HERE ifstream infile; //char mystring[6]; //char mystring[20]; int main() { infile.open("file.txt"); if(infile.fail()) { cout << " Error " << endl; } int numb_char=0; char letter; while(!infile.eof()) { infile.get(letter); cout << letter; numb_char++; break; } cout << " the number of characters is :" << numb_char << endl; infile.close(); return 0;

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  • How can i sort DESC and ASC in list generic?

    - by Phsika
    How can I sort DESC and ASC in a generic list? With LINQ and without LINQ ? I'm using vs 2008. class Program { static void Main(string[] args) { List<int> li = new List<int>(); li.Add(456); li.Add(123); li.Add(12345667); li.Add(0); li.Add(1); li.Sort(); foreach (int item in li) { Console.WriteLine(item.ToString()+"\n"); } Console.ReadKey(); } }

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  • What sort of things can cause a whole system to appear to hang for 100s-1000s of milliseconds?

    - by Ogapo
    I am working on a Windows game and while rendering, some computers will experience intermittent pauses ("hitches" for lack of a better term). When profiled they appear in seemingly random places in the code. Eventually I noticed that it wasn't just my process that was affected, but (seemingly) every process on the system. All of the threads in my application hitch at once. The CPU utilization drops during these hitches and it appears as if most processes make no progress. This leads me to believe this may be an Operating System or Driver issue, but it only occurs while playing the game (and only on some systems). What sort of operations might the operating system be doing that would require the kernel to pause all user threads and block. Some kind of I/O? At first I thought of paging but my impression is that would only affect a single process, no? Some systems in use: Windows, DirectX (3d), nVidia cards (unknown if replicates on ATI), using overlapped io for streaming

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  • Why are there two implementations of std::sort (with and without a comparator) rather than one implementation with a default template parameter?

    - by PolyVox
    In my code I'm adopting a design strategy which is similar to some standard library algorithms in that the exact behavior can be customized by a function object. The simplest example is std::sort, where a function object can control how the comparison is made between objects. I notice that the Visual C++ provides two implementations of std::sort, which naturally involves code duplication. I would have imagined that it was instead possible to have only one implementation, and provide a default comparator (using operator< ) as a default template parameter. What is the rational behind two separate versions? Would my suggestion make the interface more complex in some way? Or result in confusing error messages when the object does not provide operator Thanks, David

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  • undo or reverse argsort(), python

    - by Vincent
    Given an array 'a' I would like to sort the array by columns "a.sort(axis=0)" do some stuff to the array and then undo the sort. By that I don't mean re sort but basically reversing how each element was moved. I assume argsort() is what I need but it is not clear to me how to sort an array with the results of argsort() or more importantly apply the reverse/inverse of argsort() Here is a little more detail I have an array a, shape(a) = rXc I need to sort each column aargsort = a.argsort(axis=0) # May use this later aSort = a.sort(axis=0) now average each row aSortRM = asort.mean(axis=1) now replace each col in a row with the row mean. is there a better way than this aWithMeans = ones_like(a) for ind in range(r) # r = number of rows aWithMeans[ind]* aSortRM[ind] Now I need to undo the sort I did in the first step. ????

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  • dotNet Templated, Repeating, Databound ServerControl: Counting the templates OnDataBind?

    - by Campbeln
    I have a server control that wraps an underlying class which manages a number of indexes to track where it is in a dataset (ie: RenderedRecordCount, ErroredRecordCount, NewRecordCount, etc.). I've got the server control rendering great, but OnDataBinding I'm having an issue as to seems to happen after CreateChildControls and before Render (both of which properly manage the iteration of the underlying indexes). While I'm somewhat familiar with the ASP.NET page lifecycle, this one seems to be beyond me at the moment. So... how do I hook into the iterative process OnDataBinding uses so I can manage the underlying indexes? Will I have to iterate over the ITemplates myself, managing the indexes as I go or is there an easier solution? Also... I implemented the iteration of the underlying indexes during CreateChildControls originally in the belief that was the proper place to hook in for events like OnDataBinding (thining it was done as the controls were being .Add'd). Now it seems that this may actually be unnecessary. So I guess the secondary question is: What happens during CreateChildControls? Are the unadulterated (read: with <%-tags in place) controls added to the .Controls collection without any other processing?

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  • How do I get a array to just count how many numbers there are instead of counting the value of each number?

    - by Chad Loos
    //This is the output of the program *** start of 276 2D Arrays_03.cpp program *** Number Count Total 1 3 3 2 6 9 3 15 24 4 6 30 5 9 39 *** end of 276 2D Arrays_03.cpp program *** #include <iostream> #include <string> #include <iomanip> using namespace std; const int COLUMN_SIZE = 13; int main(void) { const int ROW_SIZE = 3; const int COUNT_SIZE = 5; void countValues(const int[][COLUMN_SIZE], const int, int[]); void display(const int [], const int); int numbers[ROW_SIZE][COLUMN_SIZE] = {{1, 3, 4, 5, 3, 2, 3, 5, 3, 4, 5, 3, 2}, {2, 1, 3, 4, 5, 3, 2, 3, 5, 3, 4, 5, 3}, {3, 4, 5, 3, 2, 1, 3, 4, 5, 3, 2, 3, 5}}; int counts[COUNT_SIZE] = {0}; string choice; cout << "*** start of 276 2D Arrays_03.cpp program ***" << endl; cout << endl; countValues(numbers, ROW_SIZE, counts); display(counts, COUNT_SIZE); cout << endl; cout << endl; cout << "*** end of 276 2D Arrays_03.cpp program ***" << endl << endl; cin.get(); return 0; } // end main() This is the function where I need to count each of the values. I know how to sum rows and cols, but I'm not quite sure of the code to just tally the values themselves. void countValues(const int numbers[][COLUMN_SIZE], const int ROW_SIZE, int counts[]) This is what I have so far. { for (int index = 0; index < ROW_SIZE; index++) counts[index]; {

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  • $_POST Variable Detected in Chrome but not in Firefox

    - by user1707973
    I am using 2 images in a form to sort out query results from the database. The form is submitted using the POST method. When i click on the first image, the query results have to be sorted in ascending order, and when i click on the second, the results have to be sorted in the descending order. This is the code for the form: <form name="" action="" method="post"> <input type="hidden" name="typep" value="price" /> <input type="image" name="sort" value="asc" src="images/asc-ar.png" /> <input type="image" name="sort" value="desc" src="images/dsc-ar.png" /> </form> Now this is the code for checking if the $_REQUEST['sort'] variable is set and therefore whether sorting is required or not. if ($_REQUEST['sort'] != "") { $sort = $_REQUEST['sort']; $typep = $_REQUEST['typep']; //query to be executed depending on values of $sort and $typep } Firefox does detect the $_REQUEST['typep'] variable but not the $_REQUEST['sort'] one. This works perfectly in Chrome though. When i test the site in Firefox, it doesn't detect the $_REQUEST['sort'] variable and therefore the if condition evaluates to false and the search results don't get sorted.

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