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  • Query next/previous record

    - by Rob
    I'm trying to find a better way to get the next or previous record from a table. Let's say I have a blog or news table: CREATE TABLE news ( news_id INT UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT, news_datestamp DATETIME NOT NULL, news_author VARCHAR(100) NOT NULL, news_title VARCHAR(100) NOT NULL, news_text MEDIUMTEXT NOT NULL ); Now on the frontend I want navigation buttons for the next or previous records, if i'm sorting by news_id, I can do something rather simple like: SELECT MIN(news_id) AS next_news_id FROM news WHERE news_id > '$old_news_id' LIMIT 1 SELECT MAX(news_id) AS prev_news_id FROM news WHERE news_id < '$old_news_id' LIMIT 1 But the news can be sorted by any field, and I don't necessarily know which field is sorted on, so this won't work if the user sorts on news_author for example. I've resorted to the rather ugly and inefficient method of sorting the entire table and looping through all records until I find the record I need. $res = mysql_query("SELECT news_id FROM news ORDER BY `$sort_column` $sort_way"); $found = $prev = $next = 0; while(list($id) = mysql_fetch_row($res)) { if($found) { $next = $id; break; } if($id == $old_news_id) { $found = true; continue; } $prev = $id; } There's got to be a better way.

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  • RichFaces a4j:support parameter passing

    - by Mark Lewis
    Hello I have a number of rich:inplaceInput tags in RichFaces which represent numbers in an array. The validator allows integers only. When a user clicks in an input and changes a value, how can I get the bean to sort the array given the new number and reRender the list of rich:inplaceInput tags so that they're in numerical order? EG <a4j:region> <rich:dataTable value="#{MyBacking.config}" var="feed" cellpadding="0" cellspacing="0" width="100%" border="0" columns="5" id="Admin"> ... <a4j:repeat... <a4j:region id="MsgCon"> <rich:inplaceInput value="#{h.id}" validator="#{MyBacking.validateID}" id="andID" showControls="true"> <a4j:support event="onviewactivated" action="#{MyBacking.sort}" reRender="Admin" /> </rich:inplaceInput> </a4j:region> </a4j:repeat> </data:Table> </a4j:region> Note I do NOT want to use dataTable sort functions. The table is complicated and I've specified id="Admin" (ie the whole table) to reRender as I've not found a way to send more localised values to the backing bean through the inplaceInput. This question is about how to use a4j:support action attribute to call the sort method so that when the reRender rerenders the component, it outputs the list in sorted order. I have the sort method working ok when I click a button to sort, but I want to have the list sorted automatically as soon as a new valid value is entered into the inplaceInput component. Thanks

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  • Is it safe to silently catch ClassCastException when searching for a specific value?

    - by finnw
    Suppose I am implementing a sorted collection (simple example - a Set based on a sorted array.) Consider this (incomplete) implementation: import java.util.*; public class SortedArraySet<E> extends AbstractSet<E> { @SuppressWarnings("unchecked") public SortedArraySet(Collection<E> source, Comparator<E> comparator) { this.comparator = (Comparator<Object>) comparator; this.array = source.toArray(); Collections.sort(Arrays.asList(array), this.comparator); } @Override public boolean contains(Object key) { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } private final Object[] array; private final Comparator<Object> comparator; } Now let's create a set of integers Set<Integer> s = new SortedArraySet<Integer>(Arrays.asList(1, 2, 3), null); And test whether it contains some specific values: System.out.println(s.contains(2)); System.out.println(s.contains(42)); System.out.println(s.contains("42")); The third line above will throw a ClassCastException. Not what I want. I would prefer it to return false (as HashSet does.) I can get this behaviour by catching the exception and returning false: @Override public boolean contains(Object key) { try { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } catch (ClassCastException e) { return false; } } Assuming the source collection is correctly typed, what could go wrong if I do this?

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  • SQL Latest photos from contacts (grouped by contact)

    - by kitsched
    Hello, To short version of this question is that I want to accomplish something along the lines of what's visible on Flickr's homepage once you're logged in. It shows the three latest photos of each of your friends sorted by date but grouped by friend. Here's a longer explanation: For example I have 3 friends: John, George and Andrea. The list I want to extract should look like this: George Photo - 2010-05-18 Photo - 2010-05-18 Photo - 2010-05-12 John Photo - 2010-05-17 Photo - 2010-05-14 Photo - 2010-05-12 Andrea Photo - 2010-05-15 Photo - 2010-05-15 Photo - 2010-05-15 Friend with most recent photo uploaded is on top but his or her 2 next files follow. I'd like to do this from MySQL, and for the time being I got here: SELECT photos.user_id, photos.id, photos.date_uploaded FROM photos WHERE photos.user_id IN (SELECT user2_id FROM user_relations WHERE user1_id = 8) ORDER BY date_uploaded DESC Where user1_id = 8 is the currently logged in user and user2_id are the ids of friends. This query indeed returns the latest files uploaded by the contacts of the user with id = 8 sorted by date. However I'd like to accomplish the grouping and limiting mentioned above. Hopefully this makes sense. Thank you in advance.

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  • MSForms.ListBox Type Mismatch in Access

    - by Jason
    I have an Access database where I use a Tab control (without tabs) to simulate a wizard. One of the tab pages has an MSForms.ListBox control called lstPorts, and a button named cmdAdd which adds the contents of a textbox to the List Box. I then try to keep the contents of the ListBox sorted. However, the call to the Sort method causes a type mismatch. Here is the cmdAdd_Click() code behind: Private Sub cmdAdd_Click() Dim test As MSForms.ListBox lstPorts2.AddItem (txtPortName) Call SortListBox(lstPorts2) End Sub Here is the SortListBox Sub: Public Sub SortListBox(ByRef oLb As MSForms.ListBox) Dim vaItems As Variant Dim i As Long, j As Long Dim vTemp As Variant 'Put the items in a variant array vaItems = oLb.List For i = LBound(vaItems, 1) To UBound(vaItems, 1) - 1 For j = i + 1 To UBound(vaItems, 1) If vaItems(i, 0) > vaItems(j, 0) Then vTemp = vaItems(i, 0) vaItems(i, 0) = vaItems(j, 0) vaItems(j, 0) = vTemp End If Next j Next i 'Clear the listbox oLb.Clear 'Add the sorted array back to the listbox For i = LBound(vaItems, 1) To UBound(vaItems, 1) oLb.AddItem vaItems(i, 0) Next i End Sub Any help out there? Since the Sort routine explicitly references the MSForms.ListBox, most of the results from Google aren't applicable. Jason

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  • question about counting sort

    - by davit-datuashvili
    hi i have write following code which prints elements in sorted order only one big problem is that it use two additional array here is my code public class occurance{ public static final int n=5; public static void main(String[]args){ // n is maximum possible value what it should be in array suppose n=5 then array may be int a[]=new int[]{3,4,4,2,1,3,5};// as u see all elements are less or equal to n //create array a.length*n int b[]=new int[a.length*n]; int c[]=new int[b.length]; for (int i=0;i<b.length;i++){ b[i]=0; c[i]=0; } for (int i=0;i<a.length;i++){ if (b[a[i]]==1){ c[a[i]]=1; } else{ b[a[i]]=1; } } for (int i=0;i<b.length;i++){ if (b[i]==1) { System.out.println(i); } if (c[i]==1){ System.out.println(i); } } } } // 1 2 3 3 4 4 5 1.i have two question what is complexity of this algorithm?i mean running time 2. how put this elements into other array with sorted order? thanks

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  • sorting a gridview in class

    - by user175084
    ok i have a project which has many gridview in its pages... now i am sorting the fridveiw using the sorting function like this: protected void GridView1_Sorting(object sender, GridViewSortEventArgs e) { DataTable dt = Session["TaskTable2"] as DataTable; if (dt != null) { //Sort the data. dt.DefaultView.Sort = e.SortExpression + " " + GetSortDirection(e.SortExpression); GridView1.DataSource = Session["TaskTable2"]; GridView1.DataBind(); } } private string GetSortDirection(string column) { // By default, set the sort direction to ascending. string sortDirection2 = "ASC"; // Retrieve the last column that was sorted. string sortExpression2 = ViewState["SortExpression2"] as string; if (sortExpression2 != null) { // Check if the same column is being sorted. // Otherwise, the default value can be returned. if (sortExpression2 == column) { string lastDirection = ViewState["SortDirection2"] as string; if ((lastDirection != null) && (lastDirection == "ASC")) { sortDirection2 = "DESC"; } } } // Save new values in ViewState. ViewState["SortDirection2"] = sortDirection2; ViewState["SortExpression2"] = column; return sortDirection2; } but this code is being repeated in many pages so i tried to put this function in a C# class and try to call it but i get errors.... for starters i get the viewstate error saying :| "viewstate does not exist in the current context" so how do i go about doing this ....?? thanks

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  • Non standard interaction among two tables to avoid very large merge

    - by riko
    Suppose I have two tables A and B. Table A has a multi-level index (a, b) and one column (ts). b determines univocally ts. A = pd.DataFrame( [('a', 'x', 4), ('a', 'y', 6), ('a', 'z', 5), ('b', 'x', 4), ('b', 'z', 5), ('c', 'y', 6)], columns=['a', 'b', 'ts']).set_index(['a', 'b']) AA = A.reset_index() Table B is another one-column (ts) table with non-unique index (a). The ts's are sorted "inside" each group, i.e., B.ix[x] is sorted for each x. Moreover, there is always a value in B.ix[x] that is greater than or equal to the values in A. B = pd.DataFrame( dict(a=list('aaaaabbcccccc'), ts=[1, 2, 4, 5, 7, 7, 8, 1, 2, 4, 5, 8, 9])).set_index('a') The semantics in this is that B contains observations of occurrences of an event of type indicated by the index. I would like to find from B the timestamp of the first occurrence of each event type after the timestamp specified in A for each value of b. In other words, I would like to get a table with the same shape of A, that instead of ts contains the "minimum value occurring after ts" as specified by table B. So, my goal would be: C: ('a', 'x') 4 ('a', 'y') 7 ('a', 'z') 5 ('b', 'x') 7 ('b', 'z') 7 ('c', 'y') 8 I have some working code, but is terribly slow. C = AA.apply(lambda row: ( row[0], row[1], B.ix[row[0]].irow(np.searchsorted(B.ts[row[0]], row[2]))), axis=1).set_index(['a', 'b']) Profiling shows the culprit is obviously B.ix[row[0]].irow(np.searchsorted(B.ts[row[0]], row[2]))). However, standard solutions using merge/join would take too much RAM in the long run. Consider that now I have 1000 a's, assume constant the average number of b's per a (probably 100-200), and consider that the number of observations per a is probably in the order of 300. In production I will have 1000 more a's. 1,000,000 x 200 x 300 = 60,000,000,000 rows may be a bit too much to keep in RAM, especially considering that the data I need is perfectly described by a C like the one I discussed above. How would I improve the performance?

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  • Getting an exception when trying to use extension method with SortedDictionary... why?

    - by Polaris878
    I'm trying to place custom objects into a sorted dictionary... I am then trying to use an extension method (Max()) on this sorted dictionary. However, I'm getting the exception: "At least one object must implement IComparable". I don't understand why I'm getting that, as my custom object obviously implements IComparable. Here is my code: public class MyDate : IComparable<MyDate> { int IComparable<MyDate>.CompareTo(MyDate obj) { if (obj != null) { if (this.Value.Ticks < obj.Value.Ticks) { return 1; } else if (this.Value.Ticks == obj.Value.Ticks) { return 0; } else { return -1; } } } public MyDate(DateTime date) { this.Value = date; } public DateTime Value; } class Program { static void Main(string[] args) { SortedDictionary<MyDate, int> sd = new SortedDictionary<MyDate,int>(); sd.Add(new MyDate(new DateTime(1)), 1); sd.Add(new MyDate(new DateTime(2)), 2); Console.WriteLine(sd.Max().Value); // Throws exception!! } } What on earth am I doing wrong???

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  • Django Aggregation Across Reverse Relationship

    - by Tom
    Given these two models: class Profile(models.Model): user = models.ForeignKey(User, unique=True, verbose_name=_('user')) about = models.TextField(_('about'), blank=True) zip = models.CharField(max_length=10, verbose_name='zip code', blank=True) website = models.URLField(_('website'), blank=True, verify_exists=False) class ProfileView(models.Model): profile = models.ForeignKey(Profile) viewer = models.ForeignKey(User, blank=True, null=True) created = models.DateTimeField(auto_now_add=True) I want to get all profiles sorted by total views. I can get a list of profile ids sorted by total views with: ProfileView.objects.values('profile').annotate(Count('profile')).order_by('-profile__count') But that's just a dictionary of profile ids, which means I then have to loop over it and put together a list of profile objects. Which is a number of additional queries and still doesn't result in a QuerySet. At that point, I might as well drop to raw SQL. Before I do, is there a way to do this from the Profile model? ProfileViews are related via a ForeignKey field, but it's not as though the Profile model knows that, so I'm not sure how to tie the two together. As an aside, I realize I could just store views as a property on the Profile model and that may turn out to be what I do here, but I'm still interested in learning how to better use the Aggregation functions.

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  • sql server - framework 4 - IIS 7 weird sort from db to page

    - by ila
    I am experiencing a strange behavior when reading a resultset from database in a calling method. The sort of the rows is different from what the database should return. My farm: - database server: sql server 2008 on a WinServer 2008 64 bit - web server: a couple of load balanced WinServer 2008 64 bit running IIS 7 The application runs on a v4.0 app pool, set to enable 32bit applications Here's a description of the problem: - a stored procedure is called, that returns a resultset sorted on a particular column - I can see thru profiler the call to the SP, if I run the statement I see correct sorting - the calling page gets the results, and before any further elaboration logs the rows immediately after the SP execution - the results are in a completely different order (I cannot even understand if they are sorted in any way) Some details on the Stored Procedure: - it is called by code using a SqlDatAdapter - it has also an output value (a count of the rows) that is read correctly - which sort field is to be used is passed as a parameter - makes use of temp tables to collect data and perform the desired sort Any idea on what I could check? Same code and same database work correctly in a test environment, 32 bit and not load balanced.

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  • facebook Hacker cup: studious Student problem.

    - by smartmuki
    During the qualification round, the following question was asked: You've been given a list of words to study and memorize. Being a diligent student of language and the arts, you've decided to not study them at all and instead make up pointless games based on them. One game you've come up with is to see how you can concatenate the words to generate the lexicographically lowest possible string. Input As input for playing this game you will receive a text file containing an integer N, the number of word sets you need to play your game against. This will be followed by N word sets, each starting with an integer M, the number of words in the set, followed by M words. All tokens in the input will be separated by some whitespace and, aside from N and M, will consist entirely of lowercase letters. Output Your submission should contain the lexicographically shortest strings for each corresponding word set, one per line and in order. Constraints 1 <= N <= 100 1 <= M <= 9 1 <= all word lengths <= 10 Example input 5 6 facebook hacker cup for studious students 5 k duz q rc lvraw 5 mybea zdr yubx xe dyroiy 5 jibw ji jp bw jibw 5 uiuy hopji li j dcyi Example output cupfacebookforhackerstudentsstudious duzklvrawqrc dyroiymybeaxeyubxzdr bwjibwjibwjijp dcyihopjijliuiuy The program I wrote goes as: chomp($numberElements=<STDIN>); for(my $i=0; $i < $numberElements; $i++) { my $string; chomp ($string = <STDIN>); my @array=split(/\s+/,$string); my $number=shift @array; @sorted=sort @array; $sortedStr=join("",@sorted); push(@data,$sortedStr); } foreach (@data) { print "$_\n"; } The program gives the correct output for the given test cases but still facebook shows it to be incorrect. Is there something wrong with the program??

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  • std::ifstream buffer caching

    - by ledokol
    Hello everybody, In my application I'm trying to merge sorted files (keeping them sorted of course), so I have to iterate through each element in both files to write the minimal to the third one. This works pretty much slow on big files, as far as I don't see any other choice (the iteration has to be done) I'm trying to optimize file loading. I can use some amount of RAM, which I can use for buffering. I mean instead of reading 4 bytes from both files every time I can read once something like 100Mb and work with that buffer after that, until there will be no element in buffer, then I'll refill the buffer again. But I guess ifstream is already doing that, will it give me more performance and is there any reason? If fstream does, maybe I can change size of that buffer? added My current code looks like that (pseudocode) // this is done in loop int i1 = input1.read_integer(); int i2 = input2.read_integer(); if (!input1.eof() && !input2.eof()) { if (i1 < i2) { output.write(i1); input2.seek_back(sizeof(int)); } else input1.seek_back(sizeof(int)); output.write(i2); } } else { if (input1.eof()) output.write(i2); else if (input2.eof()) output.write(i1); } What I don't like here is seek_back - I have to seek back to previous position as there is no way to peek 4 bytes too much reading from file if one of the streams is in EOF it still continues to check that stream instead of putting contents of another stream directly to output, but this is not a big issue, because chunk sizes are almost always equal. Can you suggest improvement for that? Thanks.

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  • Stable/repeatable random sort (MySQL, Rails)

    - by Matt Rogish
    I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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  • ASP.Net Custom Paging (w/ C#)

    - by André Alçada Padez
    Cenario: I have a GridView bound to a DataSource, every column is sortable. my main query is something like: select a, b, c, d, e, f from table order by somedate desc i added a filter form where i can define values to each one of the fields and get the results of a where form. As a result from this, i had to do a custom sorting so that when i sort by a field, i am sorting the filtered query and not the main one. Now i have to do custom paging, for the same reason, but i don't understand the philosophy of it: I want to guarantee that i can: filter the results sort by a column when i click on page 2, i get page two of the filtered and sorted results I don't know what i have to do, so i can bind the GV with this. My sorting Method, that is working just fine looks something like: string condition = GetConditions(); //gets a string like " where a>1 and b>2" depending on the filter the user defines string query = "select a, b, c, d, e, f from table "; string direction = (e.SortDirection == SortDirection.Ascending)? "asc": "desc"; string order = " order by " + e.SortExpression + " " + direction; UtilizadoresDataSource.SelectCommand = query + condition + order; i've never done custom paging, i am trying: GetConditions() //no problem here How can i find out how the GridView is sorted (by what field and sortingorder)? thank you very much

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  • Sorting in Lua, counting number of items

    - by Josh
    Two quick questions (I hope...) with the following code. The script below checks if a number is prime, and if not, returns all the factors for that number, otherwise it just returns that the number prime. Pay no attention to the zs. stuff in the script, for that is client specific and has no bearing on script functionality. The script itself works almost wonderfully, except for two minor details - the first being the factor list doesn't return itself sorted... that is, for 24, it'd return 1, 2, 12, 3, 8, 4, 6, and 24 instead of 1, 2, 3, 4, 6, 8, 12, and 24. I can't print it as a table, so it does need to be returned as a list. If it has to be sorted as a table first THEN turned into a list, I can deal with that. All that matters is the end result being the list. The other detail is that I need to check if there are only two numbers in the list or more. If there are only two numbers, it's a prime (1 and the number). The current way I have it does not work. Is there a way to accomplish this? I appreciate all the help! function get_all_factors(number) local factors = 1 for possible_factor=2, math.sqrt(number), 1 do local remainder = number%possible_factor if remainder == 0 then local factor, factor_pair = possible_factor, number/possible_factor factors = factors .. ", " .. factor if factor ~= factor_pair then factors = factors .. ", " .. factor_pair end end end factors = factors .. ", and " .. number return factors end local allfactors = get_all_factors(zs.param(1)) if zs.func.numitems(allfactors)==2 then return zs.param(1) .. " is prime." else return zs.param(1) .. " is not prime, and its factors are: " .. allfactors end

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  • Sort ranges in an array in google apps script

    - by user1637113
    I have a timesheet spreadsheet for our company and I need to sort the employees by each timesheet block (15 rows by 20 columns). I have the following code which I had help with, but the array quits sorting once it comes to a block without an employee name (I would like these to be shuffled to the bottom). Another complication I am having is there are numerous formulas in these cells and when I run it as is, it removes them. I would like to keep these intact if at all possible. Here's the code: function sortSections() { var activeSheet = SpreadsheetApp.getActiveSheet(); //SETTINGS var sheetName = activeSheet.getSheetName(); //name of sheet to be sorted var headerRows = 53; //number of header rows var pageHeaderRows = 5; //page totals to top of next emp section var sortColumn = 11; //index of column to be sorted by; 1 = column A var pageSize = 65; var sectionSize = 15; //number of rows in each section var col = sortColumn-1; var sheet = SpreadsheetApp.getActive().getSheetByName(sheetName); var data = sheet.getRange(headerRows+1, 1, sheet.getMaxRows()-headerRows, sheet.getLastColumn()).getValues(); var data3d = []; var dataLength = data.length/sectionSize; for (var i = 0; i < dataLength; i++) { data3d[i] = data.splice(0, sectionSize); } data3d.sort(function(a,b){return(((a[0][col]<b[0][col])&&a[0][col])?-1:((a[0][col]>b[0][col])?1:0))}); var sortedData = []; for (var k in data3d) { for (var l in data3d[k]) { sortedData.push(data3d[k][l]); } } sheet.getRange(headerRows+1, 1, sortedData.length, sortedData[0].length).setValues(sortedData);

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  • Insertion sort invariant assertion fails

    - by user1661211
    In the following code at the end of the for loop I use the assert function in order to test that a[i+1] is greater than or equal to a[i] but I get the following error (after the code below). Also in c++ the assert with the following seems to work just fine but in python (the following code) it does not seem to work...anyone know why? import random class Sorting: #Precondition: An array a with values. #Postcondition: Array a[1...n] is sorted. def insertion_sort(self,a): #First loop invariant: Array a[1...i] is sorted. for j in range(1,len(a)): key = a[j] i = j-1 #Second loop invariant: a[i] is the greatest value from a[i...j-1] while i >= 0 and a[i] > key: a[i+1] = a[i] i = i-1 a[i+1] = key assert a[i+1] >= a[i] return a def random_array(self,size): b = [] for i in range(0,size): b.append(random.randint(0,1000)) return b sort = Sorting() print sort.insertion_sort(sort.random_array(10)) The Error: Traceback (most recent call last): File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 27, in <module> print sort.insertion_sort(sort.random_array(10)) File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 16, in insertion_sort assert a[i+1] >= a[i] AssertionError

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  • How to create a String Array and link it to a Grade array

    - by user1861544
    I have a project that I need to create 2 Arrays, one to hold Student Names and one to hold Student Scores. The user inputs the size of the array, and the array needs to be sorted using BubbleSort (putting the high scores at the top). I have started the project, created the first array for scores, I have successfully done bubble sort and sorted the grades. Now I can't figure out how to make an array for Names, and once I do how do I make the names array correspond to the Grades array BubbleSort? Here is the code I have so far. import java.util.Scanner; public class Grades { public static void main(String[]args){ { Scanner UserIn = new Scanner(System.in); System.out.print( "How many students are there? " ); int[]GradeArray = new int[UserIn.nextInt()]; for( int i=0 ; i<GradeArray.length ; i++ ) { System.out.print( "Enter Grade for Student " + (i+1) + ": " ); GradeArray[i] = UserIn.nextInt(); } bubbleSort(GradeArray); for( int i : GradeArray ) System.out.println( i ); System.out.println(); } } private static void bubbleSort(int[]GradeArray){ int n = GradeArray.length; int temp = 0; String temp2; for(int i=0; i<n; i++){ for(int j=1; j<(n-i);j++){ if(GradeArray[j-1]<GradeArray[j]){ //swap temp=GradeArray[j-1]; GradeArray[j-1]=GradeArray[j]; GradeArray[j]=temp; } } } } } Also how do I change the grades to Double? I started with Int and when I try to change everything to double I get an error saying "Found Double, expected Int".

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  • is this correct use of jquery's document.ready?

    - by Haroldo
    The below file contains all the javascript for a page. Performance is the highest priority. Is this the most efficient way? Do all click/hover events need to to be inside the doc.ready? //DOCUMENT.READY EVENTS //--------------------------------------------------------------------------- $(function(){ // mark events as not loaded $('.event').data({ t1_loaded: false, t2_loaded: false, t3_loaded: false, art_req: false }); //mark no events have been clicked $('#wrap_right').data('first_click_made', false); // cal-block event click $('#cal_blocks div.event, #main_search div.event').live('click', function(){ var id = $(this).attr('id').split('e')[1]; event_click(id); }); // jq history $.historyInit(function(hash){ if(hash) { event_click(hash); } }); // search $('#search_input').typeWatch ({ callback: function(){ var q = $('#search_input').attr('value'); search(q); }, wait : 350, highlight : false, captureLength : 2 }); $('#search_input, #main_search div.close').live('click',function(){ $(this).attr("value",""); reset_srch_res(); }); $('#main_search').easydrag(); $('a.dialog').colorbox(); //TAB CLICK -> AJAX LOAD TAB $('#wrap_right .rs_tabs li').live('click', function(){ $this = $(this); var id = $('#wrap_right').data('curr_event'); var tab = parseInt($this.attr('rel')); //hide other tabs $('#rs_'+id+' .tab_body').hide(); //mark current(clicked) tab $('#rs_'+id+' .rs_tabs li').removeClass('curr_tab'); $this.addClass('curr_tab'); //is the tab already loaded and hidden? var loaded = $('#e'+id).data('t'+tab+'_loaded'); //console.log('id: '+id+', tab: '+tab+', loaded: '+loaded); if(loaded === true) { $('#rs_'+id+' .tab'+tab).show(); if (tab == 2) { art_requested(id); } } else { //ajax load in the tab $('#rs_'+id+' .tab'+tab).load('index_files/tab'+tab+'.php?id='+id, function(){ //after load callback if (tab == 1) { $('#rs_' + id + ' .frame').delay(600).fadeIn(600) }; if (tab == 2) { art_requested(id); } }); //mark tab as loaded $('#e'+id).data('t'+tab+'_loaded', true); //fade in current tab $('#rs_'+id+' .tab'+tab).show(); } }) }); // LOAD RS FUNCTIONS //--------------------------------------------------------------------------- function event_click(id){ window.location.hash = id; //mark current event $('#wrap_right').data('curr_event', id); //hide any other events if($('#wrap_right').data('first_click_made') === true) { $('#wrap_right .event_rs').hide(); } //frame loaded before? var loaded = $('#e'+id).data('t1_loaded'); if(loaded === true) { $('#rs_'+id).show(); } else { create_frame(id); } //open/load the first tab $('#rs_'+id+' .t1').click(); $('#wrap_right').data('first_click_made', true); $('#cal_blocks').scrollTo('#e'+id, 1000, {offset: {top:-220, left:0}}); } function create_frame(id){ var art = ents[id].art; var ven = ents[id].ven; var type = ents[id].gig_club; //select colours for tabs if(type == 1){ var label = 'gig';} else if(type == 2){ var label = 'club';} else if(type == 0){ var label = 'other';} //create rs container for this event var frame = '<div id="rs_'+id+'" class="event_rs">'; frame += '<div class="title_strip"></div>'; frame += '<div class="rs_tabs"><ul class="'+label+'"><li class="t1 nav_tab1 curr_tab hand" rel="1"></li>'; if(art == 1){frame += '<li class="t2 nav_tab2 hand" rel="2"></li>';} if(ven == 1){frame += '<li class="t3 nav_tab2 hand" rel="3"></li>';} frame += '</ul></div>'; frame += '<div id="rs_content"><div class="tab_body tab1" ></div>'; if(art == 1){frame += '<div class="tab_body tab2"></div>';} if(ven == 1){frame += '<div class="tab_body tab3"></div>';} frame += '</div>'; frame += '</div>'; $('#wrap_right').append(frame); //mark current event in cal-blocks $('#cal_blocks .event_sel').removeClass('event_sel'); $('#e'+id).addClass('event_sel'); if($('#wrap_right').data('first_click_made') === false) { $('#wrap_right').delay(500).slideDown(); $('#rs_'+id+' .rs_tabs').delay(800).fadeIn(); } }; // FUNCTIONS //--------------------------------------------------------------------------- //check to see if an artist has been requested function art_requested(id){ var art_req = $('#e'+id).data('art_req'); if(art_req !== false) { //alert(art_req); $('#art_'+art_req).click(); } } //scroll artist panes smoothly (scroll bars cause glitches otherwise) function before (){ if(!IE){$('#art_scrollable .bio_etc').css('overflow','-moz-scrollbars-none');} } function after (){ if(!IE){$('#art_scrollable .bio_etc').css('overflow','auto');} } function prep_media_carousel(){ //youtube and soundcloud player $("#rs_content .yt_scrollable a.yt, #rs_content .yt_scrollable a.sc").colorbox({ overlayClose : false, opacity : 0 }); $("#colorbox").easydrag(true); $('#cboxOverlay').remove(); } function make_carousel_scrollable(unique_id){ $('#scroll_'+unique_id).scrollable({ size:1, clickable:false, nextPage:'#r_'+unique_id, prevPage:'#l_'+unique_id }); } function check_l_r_arrows(total, counter, art_id){ //left arrow if(counter > 0) { $('#l_'+art_id).show(); $('#l_'+art_id+'_inactive').hide(); } else { $('#l_'+art_id).hide(); $('#l_'+art_id+'_inactive').show(); } //right arrow if(counter < total-3) { $('#r_'+art_id).show(); $('#r_'+art_id+'_inactive').hide(); } else { $('#r_'+art_id).hide(); $('#r_'+art_id+'_inactive').show(); } } function reset_srch_res(){ $('#main_search').fadeOut(400).children().remove(); } function search(q){ $.ajax({ type: 'GET', url: 'index_files/srch/search.php?q='+q, success: function(e) { $('#main_search').html(e).show(); } }); }

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  • Will these optimizations to my Ruby implementation of diff improve performance in a Rails app?

    - by grg-n-sox
    <tl;dr> In source version control diff patch generation, would it be worth it to use the optimizations listed at the very bottom of this writing (see <optimizations>) in my Ruby implementation of diff for making diff patches? </tl;dr> <introduction> I am programming something I have never done before and there might already be tools out there to do the exact thing I am programming but at this point I am having too much fun to care so I am still going to do it from scratch, even if there is a tool for this. So anyways, I am working on a Ruby on Rails app and need a certain feature. Basically I want each entry in a table of mine, let's say for example a table of video games, to have a stored chunk of text that represents a review or something of the sort for that table entry. However, I want this text to be both editable by any registered user and also keep track of different submissions in a version control system. The simplest solution I could think of is just implement a solution that keeps track of the text body and the diff patch history of different versions of the text body as objects in Ruby and then serialize it, preferably in human readable form (so I'll most likely use YAML for this) for editing if needed due to corruption by a software bug or a mistake is made by an admin doing some version editing. So at first I just tried to dive in head first into this feature to find that the problem of generating a diff patch is more difficult that I thought to do efficiently. So I did some research and came across some ideas. Some I have implemented already and some I have not. However, it all pretty much revolves around the longest common subsequence problem, as you would already know if you have already done anything with diff or diff-like features, and optimization the function that solves it. Currently I have it so it truncates the compared versions of the text body from the beginning and end until non-matching lines are found. Then it solves the problem using a comparison matrix, but instead of incrementing the value stored in a cell when it finds a matching line like in most longest common subsequence algorithms I have seen examples of, I increment when I have a non-matching line so as to calculate edit distance instead of longest common subsequence. Although as far as I can tell between the two approaches, they are essentially two sides of the same coin so either could be used to derive an answer. It then back-traces through the comparison matrix and notes when there was an incrementation and in which adjacent cell (West, Northwest, or North) to determine that line's diff entry and assumes all other lines to be unchanged. Normally I would leave it at that, but since this is going into a Rails environment and not just some stand-alone Ruby script, I started getting worried about needing to optimize at least enough so if a spammer that somehow knew how I implemented the version control system and knew my worst case scenario entry still wouldn't be able to hit the server that bad. After some searching and reading of research papers and articles through the internet, I've come across several that seem decent but all seem to have pros and cons and I am having a hard time deciding how well in this situation that the pros and cons balance out. So are the ones listed here worth it? I have listed them with known pros and cons. </introduction> <optimizations> Chop the compared sequences into multiple chucks of subsequences by splitting where lines are unchanged, and then truncating each section of unchanged lines at the beginning and end of each section. Then solve the edit distance of each subsequence. Pro: Changes the time increase as the changed area gets bigger from a quadratic increase to something more similar to a linear increase. Con: Figuring out where to split already seems like you have to solve edit distance except now you don't care how it is changed. Would be fine if this was solvable by a process closer to solving hamming distance but a single insertion would throw this off. Use a cryptographic hash function to both convert all sequence elements into integers and ensure uniqueness. Then solve the edit distance comparing the hash integers instead of the sequence elements themselves. Pro: The operation of comparing two integers is faster than the operation of comparing two strings, so a slight performance gain is received after every comparison, which can be a lot overall. Con: Using a cryptographic hash function takes time to convert all the sequence elements and may end up costing more time to do the conversion that you gain back from the integer comparisons. You could use the built in hash function for a string but that will not guarantee uniqueness. Use lazy evaluation to only calculate the three center-most diagonals of the comparison matrix and then only calculate additional diagonals as needed. And then also use this approach to possibly remove the need on some comparisons to compare all three adjacent cells as desribed here. Pro: Can turn an algorithm that always takes O(n * m) time and make it so only worst case scenario is that time, best case becomes practically linear, and average case is somewhere between the two. Con: It is an algorithm I've only seen implemented in functional programming languages and I am having a difficult time comprehending how to convert this into Ruby based on how it is described at the site linked to above. Make a C module and do the hard work at the native level in C and just make a Ruby wrapper for it so Ruby can make all the calls to it that it needs. Pro: I have to imagine that evaluating something like this in could be a LOT faster. Con: I have no idea how Rails handles apps with ruby code that has C extensions and it hurts the portability of the app. This is an optimization for after the solving of edit distance, but idea is to store additional combined diffs with the ones produced by each version to make a delta-tree data structure with the most recently made diff as the root node of the tree so getting to any version takes worst case time of O(log n) instead of O(n). Pro: Would make going back to an old version a lot faster. Con: It would mean every new commit, the delta-tree would get a new root node that will cost time to reorganize the delta-tree for an operation that will be carried out a lot more often than going back a version, not to mention the unlikelihood it will be an old version. </optimizations> So are these things worth the effort?

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  • How do I control the direction of the scroll on my coda slider?

    - by lightingwrist
    Hello, I have a coda slider and am unable to determine the direction of the scroll. I have 3 panels that I want to scroll left to right. Sometimes it scrolls left to right, sometimes up and down, and sometimes horizontally. How do I lock it down to go the direction I want? Here is the HTML: <body> <div id="slider_home" class="round_10px"> <ul class="navigation_home"> <li><a href="#scroll_Parents" class="round_10px">Information For Parents</a></li> <li><a href="#scroll_Materials" class="round_10px">Print Materials</a></li> <li><a href="#scroll_Resources" class="round_10px">Online Resources</a></li> </ul> <div id="scroll_bg_home"> <div class="scroll_home"> <div class="scrollContainer_home"> <div class="panel_home" id="scroll_Parents"> content </div> <div class="panel_home" id="scroll_Materials"> content </div> <div class="panel_home" id="scroll_Resources"> content </div> </div> </div> </div> </div> </body> Here is the CSS: #wrapper {width:550px;margin:0px auto;} #intro {padding-bottom:10px;} h2 {margin:0;margin-bottom:14px;padding:0;} #slider {width:631px;margin:10px auto 0px auto;position:relative;} #scroll_bg{height:360px;width:590px;overflow:hidden;position:relative;clear:left;background:#FFFFFF url(images/) no-repeat; margin:0px auto 0px auto} .scroll{ background:transparent; width:550px; height:370px; padding:0px; margin:0px auto; overflow:hidden; } .scrollContainer div.panel {padding:20px 0px;height:330px; width:550px;margin:0px;float:left;} #shade {background:#EDEDEC url(images/shade.jpg) no-repeat 0 0;height:50px;} ul.navigation {list-style:none;margin:0px 0px 0px 23px;padding:0px;padding-bottom:0px;} ul.navigation li {display:inline; margin-right:5px;} ul.navigation li a { background:#FFFFFF;font-family:Arial, Helvetica, sans-serif; font-size:16px; font-weight:bold; color:#CCCCCC;padding:5px 5px 5px 5px;border:1px #F4F4F4 solid;text-decoration: none;} ul.navigation a:hover { color:#EDEDEC;border:1px #E6E6E6 solid;} ul.navigation a.selected {color:#333333;} ul.navigation a:focus {outline:none;} .scrollButtons {position:absolute;top:150px;cursor:pointer;} .scrollButtons.left {left:-37px;top:20px} .scrollButtons.right {right:-32px;top:20px;} .hide {display:none;} And here is the Jquery includes file: // when the DOM is ready... $(document).ready(function () { var $panels = $('#slider_home .scrollContainer_home > div.panel_home'); var $container = $('#slider_home .scrollContainer_home'); // if true, we'll float all the panels left and fix the width // of the container var horizontal = true; // float the panels left if we're going horizontal if (horizontal) { $panels.css({ 'float' : 'left', 'position' : 'relative' // IE fix to ensure overflow is hidden }); // calculate a new width for the container (so it holds all panels) $container.css('width', $panels[0].offsetWidth * $panels.length); } // collect the scroll object, at the same time apply the hidden overflow // to remove the default scrollbars that will appear var $scroll_bg = $('#scroll_bg_home'); var $scroll = $('#slider_home .scroll_home').css('overflow', 'hidden'); // apply our left + right buttons $scroll_bg .before('<img class="scrollButtons_home left" src="styles/images/BackFlip.jpg" />') .after('<img class="scrollButtons_home right" src="styles/images/flipForward.jpg" />'); // handle nav selection function selectNav() { $(this) .parents('ul:first') .find('a') .removeClass('selected') .end() .end() .addClass('selected'); } $('.navigation_home').find('a').click(selectNav); // go find the navigation link that has this target and select the nav function trigger(data) { var el = $('.navigation_home').find('a[href$="' + data.id + '"]').get(0); selectNav.call(el); } if (window.location.hash) { trigger({ id : window.location.hash.substr(1) }); } else { $('.navigation_home a:first').click(); } // offset is used to move to *exactly* the right place, since I'm using // padding on my example, I need to subtract the amount of padding to // the offset. Try removing this to get a good idea of the effect var offset = parseInt((horizontal ? $container.css('paddingTop') : $container.css('paddingLeft')) || 0) * -1; var scrollOptions = { target: $scroll, // the element that has the overflow // can be a selector which will be relative to the target items: $panels, navigation: '.navigation_home a', // selectors are NOT relative to document, i.e. make sure they're unique prev: 'img.left', next: 'img.right', // allow the scroll effect to run both directions axis: 'xy', onAfter: trigger, // our final callback offset: offset, // duration of the sliding effect duration: 500, // easing - can be used with the easing plugin: // http://gsgd.co.uk/sandbox/jquery/easing/ easing: 'swing' }; // apply serialScroll to the slider - we chose this plugin because it // supports// the indexed next and previous scroll along with hooking // in to our navigation. $('#slider_home').serialScroll(scrollOptions); // now apply localScroll to hook any other arbitrary links to trigger // the effect $.localScroll(scrollOptions); // finally, if the URL has a hash, move the slider in to position, // setting the duration to 1 because I don't want it to scroll in the // very first page load. We don't always need this, but it ensures // the positioning is absolutely spot on when the pages loads. scrollOptions.duration = 1; $.localScroll.hash(scrollOptions); });

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  • C#/.NET Fundamentals: Choosing the Right Collection Class

    - by James Michael Hare
    The .NET Base Class Library (BCL) has a wide array of collection classes at your disposal which make it easy to manage collections of objects. While it's great to have so many classes available, it can be daunting to choose the right collection to use for any given situation. As hard as it may be, choosing the right collection can be absolutely key to the performance and maintainability of your application! This post will look at breaking down any confusion between each collection and the situations in which they excel. We will be spending most of our time looking at the System.Collections.Generic namespace, which is the recommended set of collections. The Generic Collections: System.Collections.Generic namespace The generic collections were introduced in .NET 2.0 in the System.Collections.Generic namespace. This is the main body of collections you should tend to focus on first, as they will tend to suit 99% of your needs right up front. It is important to note that the generic collections are unsynchronized. This decision was made for performance reasons because depending on how you are using the collections its completely possible that synchronization may not be required or may be needed on a higher level than simple method-level synchronization. Furthermore, concurrent read access (all writes done at beginning and never again) is always safe, but for concurrent mixed access you should either synchronize the collection or use one of the concurrent collections. So let's look at each of the collections in turn and its various pros and cons, at the end we'll summarize with a table to help make it easier to compare and contrast the different collections. The Associative Collection Classes Associative collections store a value in the collection by providing a key that is used to add/remove/lookup the item. Hence, the container associates the value with the key. These collections are most useful when you need to lookup/manipulate a collection using a key value. For example, if you wanted to look up an order in a collection of orders by an order id, you might have an associative collection where they key is the order id and the value is the order. The Dictionary<TKey,TVale> is probably the most used associative container class. The Dictionary<TKey,TValue> is the fastest class for associative lookups/inserts/deletes because it uses a hash table under the covers. Because the keys are hashed, the key type should correctly implement GetHashCode() and Equals() appropriately or you should provide an external IEqualityComparer to the dictionary on construction. The insert/delete/lookup time of items in the dictionary is amortized constant time - O(1) - which means no matter how big the dictionary gets, the time it takes to find something remains relatively constant. This is highly desirable for high-speed lookups. The only downside is that the dictionary, by nature of using a hash table, is unordered, so you cannot easily traverse the items in a Dictionary in order. The SortedDictionary<TKey,TValue> is similar to the Dictionary<TKey,TValue> in usage but very different in implementation. The SortedDictionary<TKey,TValye> uses a binary tree under the covers to maintain the items in order by the key. As a consequence of sorting, the type used for the key must correctly implement IComparable<TKey> so that the keys can be correctly sorted. The sorted dictionary trades a little bit of lookup time for the ability to maintain the items in order, thus insert/delete/lookup times in a sorted dictionary are logarithmic - O(log n). Generally speaking, with logarithmic time, you can double the size of the collection and it only has to perform one extra comparison to find the item. Use the SortedDictionary<TKey,TValue> when you want fast lookups but also want to be able to maintain the collection in order by the key. The SortedList<TKey,TValue> is the other ordered associative container class in the generic containers. Once again SortedList<TKey,TValue>, like SortedDictionary<TKey,TValue>, uses a key to sort key-value pairs. Unlike SortedDictionary, however, items in a SortedList are stored as an ordered array of items. This means that insertions and deletions are linear - O(n) - because deleting or adding an item may involve shifting all items up or down in the list. Lookup time, however is O(log n) because the SortedList can use a binary search to find any item in the list by its key. So why would you ever want to do this? Well, the answer is that if you are going to load the SortedList up-front, the insertions will be slower, but because array indexing is faster than following object links, lookups are marginally faster than a SortedDictionary. Once again I'd use this in situations where you want fast lookups and want to maintain the collection in order by the key, and where insertions and deletions are rare. The Non-Associative Containers The other container classes are non-associative. They don't use keys to manipulate the collection but rely on the object itself being stored or some other means (such as index) to manipulate the collection. The List<T> is a basic contiguous storage container. Some people may call this a vector or dynamic array. Essentially it is an array of items that grow once its current capacity is exceeded. Because the items are stored contiguously as an array, you can access items in the List<T> by index very quickly. However inserting and removing in the beginning or middle of the List<T> are very costly because you must shift all the items up or down as you delete or insert respectively. However, adding and removing at the end of a List<T> is an amortized constant operation - O(1). Typically List<T> is the standard go-to collection when you don't have any other constraints, and typically we favor a List<T> even over arrays unless we are sure the size will remain absolutely fixed. The LinkedList<T> is a basic implementation of a doubly-linked list. This means that you can add or remove items in the middle of a linked list very quickly (because there's no items to move up or down in contiguous memory), but you also lose the ability to index items by position quickly. Most of the time we tend to favor List<T> over LinkedList<T> unless you are doing a lot of adding and removing from the collection, in which case a LinkedList<T> may make more sense. The HashSet<T> is an unordered collection of unique items. This means that the collection cannot have duplicates and no order is maintained. Logically, this is very similar to having a Dictionary<TKey,TValue> where the TKey and TValue both refer to the same object. This collection is very useful for maintaining a collection of items you wish to check membership against. For example, if you receive an order for a given vendor code, you may want to check to make sure the vendor code belongs to the set of vendor codes you handle. In these cases a HashSet<T> is useful for super-quick lookups where order is not important. Once again, like in Dictionary, the type T should have a valid implementation of GetHashCode() and Equals(), or you should provide an appropriate IEqualityComparer<T> to the HashSet<T> on construction. The SortedSet<T> is to HashSet<T> what the SortedDictionary<TKey,TValue> is to Dictionary<TKey,TValue>. That is, the SortedSet<T> is a binary tree where the key and value are the same object. This once again means that adding/removing/lookups are logarithmic - O(log n) - but you gain the ability to iterate over the items in order. For this collection to be effective, type T must implement IComparable<T> or you need to supply an external IComparer<T>. Finally, the Stack<T> and Queue<T> are two very specific collections that allow you to handle a sequential collection of objects in very specific ways. The Stack<T> is a last-in-first-out (LIFO) container where items are added and removed from the top of the stack. Typically this is useful in situations where you want to stack actions and then be able to undo those actions in reverse order as needed. The Queue<T> on the other hand is a first-in-first-out container which adds items at the end of the queue and removes items from the front. This is useful for situations where you need to process items in the order in which they came, such as a print spooler or waiting lines. So that's the basic collections. Let's summarize what we've learned in a quick reference table.  Collection Ordered? Contiguous Storage? Direct Access? Lookup Efficiency Manipulate Efficiency Notes Dictionary No Yes Via Key Key: O(1) O(1) Best for high performance lookups. SortedDictionary Yes No Via Key Key: O(log n) O(log n) Compromise of Dictionary speed and ordering, uses binary search tree. SortedList Yes Yes Via Key Key: O(log n) O(n) Very similar to SortedDictionary, except tree is implemented in an array, so has faster lookup on preloaded data, but slower loads. List No Yes Via Index Index: O(1) Value: O(n) O(n) Best for smaller lists where direct access required and no ordering. LinkedList No No No Value: O(n) O(1) Best for lists where inserting/deleting in middle is common and no direct access required. HashSet No Yes Via Key Key: O(1) O(1) Unique unordered collection, like a Dictionary except key and value are same object. SortedSet Yes No Via Key Key: O(log n) O(log n) Unique ordered collection, like SortedDictionary except key and value are same object. Stack No Yes Only Top Top: O(1) O(1)* Essentially same as List<T> except only process as LIFO Queue No Yes Only Front Front: O(1) O(1) Essentially same as List<T> except only process as FIFO   The Original Collections: System.Collections namespace The original collection classes are largely considered deprecated by developers and by Microsoft itself. In fact they indicate that for the most part you should always favor the generic or concurrent collections, and only use the original collections when you are dealing with legacy .NET code. Because these collections are out of vogue, let's just briefly mention the original collection and their generic equivalents: ArrayList A dynamic, contiguous collection of objects. Favor the generic collection List<T> instead. Hashtable Associative, unordered collection of key-value pairs of objects. Favor the generic collection Dictionary<TKey,TValue> instead. Queue First-in-first-out (FIFO) collection of objects. Favor the generic collection Queue<T> instead. SortedList Associative, ordered collection of key-value pairs of objects. Favor the generic collection SortedList<T> instead. Stack Last-in-first-out (LIFO) collection of objects. Favor the generic collection Stack<T> instead. In general, the older collections are non-type-safe and in some cases less performant than their generic counterparts. Once again, the only reason you should fall back on these older collections is for backward compatibility with legacy code and libraries only. The Concurrent Collections: System.Collections.Concurrent namespace The concurrent collections are new as of .NET 4.0 and are included in the System.Collections.Concurrent namespace. These collections are optimized for use in situations where multi-threaded read and write access of a collection is desired. The concurrent queue, stack, and dictionary work much as you'd expect. The bag and blocking collection are more unique. Below is the summary of each with a link to a blog post I did on each of them. ConcurrentQueue Thread-safe version of a queue (FIFO). For more information see: C#/.NET Little Wonders: The ConcurrentStack and ConcurrentQueue ConcurrentStack Thread-safe version of a stack (LIFO). For more information see: C#/.NET Little Wonders: The ConcurrentStack and ConcurrentQueue ConcurrentBag Thread-safe unordered collection of objects. Optimized for situations where a thread may be bother reader and writer. For more information see: C#/.NET Little Wonders: The ConcurrentBag and BlockingCollection ConcurrentDictionary Thread-safe version of a dictionary. Optimized for multiple readers (allows multiple readers under same lock). For more information see C#/.NET Little Wonders: The ConcurrentDictionary BlockingCollection Wrapper collection that implement producers & consumers paradigm. Readers can block until items are available to read. Writers can block until space is available to write (if bounded). For more information see C#/.NET Little Wonders: The ConcurrentBag and BlockingCollection Summary The .NET BCL has lots of collections built in to help you store and manipulate collections of data. Understanding how these collections work and knowing in which situations each container is best is one of the key skills necessary to build more performant code. Choosing the wrong collection for the job can make your code much slower or even harder to maintain if you choose one that doesn’t perform as well or otherwise doesn’t exactly fit the situation. Remember to avoid the original collections and stick with the generic collections.  If you need concurrent access, you can use the generic collections if the data is read-only, or consider the concurrent collections for mixed-access if you are running on .NET 4.0 or higher.   Tweet Technorati Tags: C#,.NET,Collecitons,Generic,Concurrent,Dictionary,List,Stack,Queue,SortedList,SortedDictionary,HashSet,SortedSet

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  • How to UNIX sort by one column only?

    - by ssn
    I know that the -k option for the Unix sort allow us to sort by a specific column and all of the following. For instance, given the input file: 2 3 2 2 1 2 2 1 1 1 Using sort -n -k 1, I get an output sorted by the 1st column and then by the 2nd: 1 1 1 2 2 1 2 2 2 3 However, I want to keep the 2nd column ordering, like this: 1 2 1 1 2 3 2 2 2 1 Is this possible with the sort command?

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  • How can I sort Windows 7 control panel by columns, not rows

    - by user26453
    As best as I can tell the behavior of Windows 7's control panel is as follows: When Large Icons or Small Icons display modes are used, the icons are sorted alphabetically. However they are ordered by row: a b c d e f g h as opposed to what I usually expect in any file browser: a d g b e h c f Why is this the one part of Windows 7 that behaves this way and is there any way to change this behavior?

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