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  • Concatinate integer arrays iteratively

    - by Ojtwist
    I have a methode in2.getImagesOneDim() which gives me an array of integers, to be more precise the pixel values of an image. Now i want to create one big array with all the pixel values of all the images. Therefore I have to call this method several times. Now I would like to concatenate the previous output to the current output until all images are read. In some kind of pseudo code, where the + is a concatination ... : for (int i = 1; i < 25; i++) { ConArray = ConArray + in2.getImagesOneDim("../images/"+i); } How would I do this in java ?

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  • Javascript Inheritance and Arrays

    - by Inespe
    Hi all! I am trying to define a javascript class with an array property, and its subclass. The problem is that all instances of the subclass somehow "share" the array property: // class Test function Test() { this.array = []; this.number = 0; } Test.prototype.push = function() { this.array.push('hello'); this.number = 100; } // class Test2 : Test function Test2() { } Test2.prototype = new Test(); var a = new Test2(); a.push(); // push 'hello' into a.array var b = new Test2(); alert(b.number); // b.number is 0 - that's OK alert(b.array); // but b.array is containing 'hello' instead of being empty. why? As you can see I don't have this problem with primitive data types... Any suggestions?

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  • Help with PHP and associative arrays

    - by errata
    Hello. I have to do a simple calculator in php based on user's input and choice from select field, something like this: <?php $a = $_GET['a']; $b = $_GET['b']; $array = array( "option1" => 0.1, "option2" => 0.15, "option3" => 0.3, "option4" => 3, "option5" => 3, "option6" => 16, "option7" => 16, "option8" => 16 ); echo "<form action='calc.php' method='get'>"; echo "<input type='text' name='a' value='".$a."'> of "; echo "<select name='b'>"; foreach ($array as $k => $v) { echo "<option value='".$v."'>".$k."</option>"; } echo "</select> "; echo "<input type='submit' value='='> "; $total_volume = $a * $b; echo $total_volume; echo "</form>"; ?> Well, for now everything works fine, but the idea is that after user submits form, the page reloads with sent amount in input field and selected option which user actually selected... First thing is easy: I just put value="a" in my input field, but I'm not sure how to make a selected option in <select> field??? I started with this: foreach ($array as $k => $v) { echo "<option value='".$v."'"; if ($b == $v) { echo " selected "; } echo ">".$k."</option>"; } ...but this is obviously not working as expected... Please help me with this easy one :) Thanks!

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  • PHP - Patterns within Arrays

    - by Toby
    I am trying to create a function which maps a recurring pattern of integers using an array. As an example if I have a starting array of (0,1,3) and I know that I want to stop the pattern when I hit 15. The pattern gets incremented by a fixed integer each time (lets say 4) so my final pattern should be.. 0 1 3 4 (0 + 4) 5 (1 + 4) 7 (2 + 4) 8 (4 + 4) 9 (5 + 4) 11(7 + 4) 12(8 + 4) 13(9 + 4) 15(11+ 4) Does anyone have any pointers on how this can be achieved? My current implementation works but is stupidly inefficient which something like this... $array = array(0,1,3); $inc = 4; $end = end($array); $final = 15; while($end < $final) { $tmp = array(); foreach($array AS $row) { $tmp = $row + $inc; } $array = merge($tmp, $array); $end = end($array); }

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  • Subtype polymorphism and arrays

    - by user133466
    Computer[] labComputers = new Computer[10]; with public class Computer { ... void toString(){ // print computer specs } } public class Notebook extends Computer{ ... void toString(){ // print computer specs + laptop color } } each subscripted variable labComputers[i] can reference either a Computer object or a Notebook object because Notebook is a subclass of Computer. For the method call labComputers[i].toString(), polymorphism ensures that the correct toString method is called. I wonder what if we do Notebook[] labComputers = new Notebook[10]; what kind or error would I get if I reference with Computer object and a Notebook object

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  • looping and arrays

    - by user1838418
    Hi I'm trying to construct a loop to execute 16 states of the 8 4 2 1 code in (C++) while( condition) { double Bubble[16], Bubble1[16]; Bubble[0] = ( a-2 - (b-2) ) + ( c-2 - (d-2)); // represents 0000 Bubble[1] = ( a-2 - (b-2) ) + ( c-2 - (d+2)); // represents 0001 Bubble[2] = ( a-2 - (b-2) ) + ( c+2 - (d-2)); // represents 0010 Bubble[3] = ( a-2 - (b-2) ) + ( c+2 - (d+2)); //represents 0011 ....... Bubble[15] =(a+2 - (b+2) ) + ( c+2 - (d+2)); //represents 1111 } Is there an easy way of coding using for loops? instead of writing bubble[] every time? 0 stands for -2 and 1 stands for +2. So I have 4 variables and each one need to be incremented and/or decremented. Can this be done using for loop? Appreciate your help

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  • C++ Arrays manipulations (python-like operations)

    - by Linai
    Hi Guys, I'm trying to figure out the best C++ library/package for array manipulations in a manner of python. Basically I need a simplicity like this: values = numpy.array(inp.data) idx1 = numpy.where(values > -2.14) idx2 = numpy.where(values < 2.0) res1 = (values[idx1] - diff1)/1000 res1 = (values[idx2] - diff2)*1000 In python it's just 5 lines, but the simplest way in C++ i can think of is quite a number of nested loops. Pls advise..

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  • Declaring arrays in c language without initial size

    - by user2534857
    this is the question-- Write a program to manipulate the temperature details as given below. - Input the number of days to be calculated. – Main function - Input temperature in Celsius – input function - Convert the temperature from Celsius to Fahrenheit.- Separate function - find the average temperature in Fahrenheit. how can I make this program without initial size of array ?? #include<stdio.h> #include<conio.h> void input(int); int temp[10]; int d; void main() { int x=0; float avg=0,t=0; printf("\nHow many days : "); scanf("%d",&d); input(d); conv(); for(x=0;x<d;x++) { t=t+temp[x]; } avg=t/d; printf("Avarage is %f",avg); getch(); } void input(int d) { int x=0; for(x=0;x<d;x++) { printf("Input temperature in Celsius for #%d day",x+1); scanf("%d",&temp[x]); } } void conv() { int x=0; for(x=0;x<d;x++) { temp[x]=1.8*temp[x]+32; } }

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  • Comparing arrays with sql

    - by Nissim
    I want to perform a 'SELECT' statement with a byte array (binary) parameter as a condition. I tried to google it, but didn't find anything useful. In general, I keep information of files in the database. one of the properties is the file's hash (binary). I want to give a hash to the SELECT statement, and get all rows with the same hash value.

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  • C Allocating Two Dimensional Arrays

    - by Jacob
    I am trying to allocate a 2D dimension array of File Descriptors... So I would need something like this fd[0][0] fd[0][1] I have coded so far: void allocateMemory(int row, int col, int ***myPipes){ int i = 0,i2 = 0; myPipes = (int**)malloc(row * sizeof(int*)); for(i = 0; i < row;i++){ myPipes[i] = (int*)malloc(col * sizeof(int)); } } How can I set it all too zeros right now I keep getting a seg fault when I try to assign a value... Thanks

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  • Loop crashing program having to do with 2D arrays

    - by user450062
    I am creating an encoding program and when I instruct the program to create a 5X5 grid based on the alphabet while skipping over letters that match up to certain pre-defined variables(which are given values by user input during runtime). I have a loop that instructs the loop to keep running until the values that access the array are out of bounds, the loop seems to cause the problem. This code is standardized so there shouldn't be much trouble compiling it in another compiler. Also would it be better to seperate my program into functions? here is the code: #include<iostream> #include<fstream> #include<cstdlib> #include<string> #include<limits> using namespace std; int main(){ while (!cin.fail()) { char type[81]; char filename[20]; char key [5]; char f[2] = "q"; char g[2] = "q"; char h[2] = "q"; char i[2] = "q"; char j[2] = "q"; char k[2] = "q"; char l[2] = "q"; int a = 1; int b = 1; int c = 1; int d = 1; int e = 1; string cipherarraytemplate[5][5]= { {"a","b","c","d","e"}, {"f","g","h","i","j"}, {"k","l","m","n","o"}, {"p","r","s","t","u"}, {"v","w","x","y","z"} }; string cipherarray[5][5]= { {"a","b","c","d","e"}, {"f","g","h","i","j"}, {"k","l","m","n","o"}, {"p","r","s","t","u"}, {"v","w","x","y","z"} }; cout<<"Enter the name of a file you want to create.\n"; cin>>filename; ofstream outFile; outFile.open(filename); outFile<<fixed; outFile.precision(2); outFile.setf(ios_base::showpoint); cin.ignore(std::numeric_limits<int>::max(),'\n'); cout<<"enter your codeword(codeword can have no repeating letters)\n"; cin>>key; while (key[a] != '\0' ){ while(b < 6){ cipherarray[b][c] = key[a]; if ( f == "q" ) { cipherarray[b][c] = f; } if ( f != "q" && g == "q" ) { cipherarray[b][c] = g; } if ( g != "q" && h == "q" ) { cipherarray[b][c] = h; } if ( h != "q" && i == "q" ) { cipherarray[b][c] = i; } if ( i != "q" && j == "q" ) { cipherarray[b][c] = j; } if ( j != "q" && k == "q" ) { cipherarray[b][c] = k; } if ( k != "q" && l == "q" ) { cipherarray[b][c] = l; } a++; b++; } c++; b = 1; } while (c < 6 || b < 6){ if (cipherarraytemplate[d][e] == f || cipherarraytemplate[d][e] == g || cipherarraytemplate[d][e] == h || cipherarraytemplate[d][e] == i || cipherarraytemplate[d][e] == j || cipherarraytemplate[d][e] == k || cipherarraytemplate[d][e] == l){ d++; } else { cipherarray[b][c] = cipherarraytemplate[d][e]; d++; b++; } if (d == 6){ d = 1; e++; } if (b == 6){ c++; b = 1; } } cout<<"now enter some text."<<endl<<"To end this program press Crtl-Z\n"; while(!cin.fail()){ cin.getline(type,81); outFile<<type<<endl; } outFile.close(); } } I know there is going to be some mid-forties guy out there who is going to stumble on to this post, he's have been programming for 20-some years and he's going to look at my code and say: "what is this guy doing".

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  • abstract data type list. . .

    - by aldrin
    A LIST is an ordered collection of items where items may be inserted anywhere in the list. Implement a LIST using an array as follows: struct list { int *items; // pointer to the array int size; // actual size of the array int count; // number of items in the array }; typedef struct list *List; // pointer to the structure Implement the following functions: a) List newList(int size); - will create a new List and return its pointer. Allocate space for the structure, allocate space for the array, then initialize size and count, return the pointer. b) void isEmpty(List list); c) void display(List list); d) int contains(List list, int item); e) void remove(List list, int i) ; f) void insertAfter(List list,int item, int i); g) void addEnd(List list,int item) - add item at the end of the list – simply store the data at position count, then increment count. If the array is full, allocate an array twice as big as the original. count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 addEnd(list,40) will result to count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 40 h) void addFront(List list,int item) - shift all elements to the right so that the item can be placed at position 0, then increment count. Bonus: if the array is full, allocate an array twice as big as the original. count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 addFront(list,40) will result to count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 10 15 20 30 i) void removeFront(List list) - shift all elements to the left and decrement count; count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 10 15 20 30 removeFront(list) will result to count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 j) void remove(List list,int item) - get the index of the item in the list and then shift all elements to the count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 10 15 20 30 remove(list,10) will result to count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 15 20 30

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  • How to find unique values in jagged array

    - by David Liddle
    I would like to know how I can count the number of unique values in a jagged array. My domain object contains a string property that has space delimitered values. class MyObject { string MyProperty; //e.g = "v1 v2 v3" } Given a list of MyObject's how can I determine the number of unique values? The following linq code returns an array of jagged array values. A solution would be to store a temporary single array of items, looped through each jagged array and if values do not exist, to add them. Then a simple count would return the unique number of values. However, was wondering if there was a nicer solution. db.MyObjects.Where(t => !String.IsNullOrEmpty(t.MyProperty)) .Select(t => t.Categories.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)) .ToArray() Below is a more readable example: array[0] = { "v1", "v2", "v3" } array[1] = { "v1" } array[2] = { "v4", "v2" } array[3] = { "v1", "v5" } From all values the unique items are v1, v2, v3, v4, v5. The total number of unique items is 5. Is there a solution, possibly using linq, that returns either only the unique values or returns the number of unique values?

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  • Delphi SetLength Custom Indexing

    - by Andreas Rejbrand
    In Delphi, it is possible to create an array of the type var Arr: array[2..N] of MyType; which is an array of N - 1 elements indexed from 2 to N. If we instead declare a dynamic array var Arr: array of MyType and later allocate N - 1 elements by means of SetLength(Arr, N - 1) then the elements will be indexed from 0 to N - 2. Is it possible to make them indexed from 2 to N (say) instead?

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  • Configuration Manager sub site codes

    - by NA Slacker
    I have two sub-sites set up in configuration manager. When the SCCM agent installs on the client machines within the boundaries of those sub sites they are assigned the site code of the Primary site, not the sub site code. As a result their management server remains the main server not the sub site server. I am setting up thes sub sites on cross WAN locations to cut down on traffic. What could be preventing the clients from getting associated with the proper sub site code.

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  • Inserting and Deleting Sub Rows in GridView

    - by Vincent Maverick Durano
    A user in the forums (http://forums.asp.net) is asking how to insert  sub rows in GridView and also add delete functionality for the inserted sub rows. In this post I'm going to demonstrate how to this in ASP.NET WebForms.  The basic idea to achieve this is we just need to insert row data in the DataSource that is being used in GridView since the GridView rows will be generated based on the DataSource data. To make it more clear then let's build up a sample application. To start fire up Visual Studio and create a WebSite or Web Application project and then add a new WebForm. In the WebForm ASPX page add this GridView markup below:   1: <asp:gridview ID="GridView1" runat="server" AutoGenerateColumns="false" onrowdatabound="GridView1_RowDataBound"> 2: <Columns> 3: <asp:BoundField DataField="RowNumber" HeaderText="Row Number" /> 4: <asp:TemplateField HeaderText="Header 1"> 5: <ItemTemplate> 6: <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> 7: </ItemTemplate> 8: </asp:TemplateField> 9: <asp:TemplateField HeaderText="Header 2"> 10: <ItemTemplate> 11: <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox> 12: </ItemTemplate> 13: </asp:TemplateField> 14: <asp:TemplateField HeaderText="Header 3"> 15: <ItemTemplate> 16: <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox> 17: </ItemTemplate> 18: </asp:TemplateField> 19: <asp:TemplateField HeaderText="Action"> 20: <ItemTemplate> 21: <asp:LinkButton ID="LinkButton1" runat="server" onclick="LinkButton1_Click" Text="Insert"></asp:LinkButton> 22: </ItemTemplate> 23: </asp:TemplateField> 24: </Columns> 25: </asp:gridview>   Then at the code behind source of ASPX page you can add this codes below:   1: private DataTable FillData() { 2:   3: DataTable dt = new DataTable(); 4: DataRow dr = null; 5:   6: //Create DataTable columns 7: dt.Columns.Add(new DataColumn("RowNumber", typeof(string))); 8:   9: //Create Row for each columns 10: dr = dt.NewRow(); 11: dr["RowNumber"] = 1; 12: dt.Rows.Add(dr); 13:   14: dr = dt.NewRow(); 15: dr["RowNumber"] = 2; 16: dt.Rows.Add(dr); 17:   18: dr = dt.NewRow(); 19: dr["RowNumber"] = 3; 20: dt.Rows.Add(dr); 21:   22: dr = dt.NewRow(); 23: dr["RowNumber"] = 4; 24: dt.Rows.Add(dr); 25:   26: dr = dt.NewRow(); 27: dr["RowNumber"] = 5; 28: dt.Rows.Add(dr); 29:   30: //Store the DataTable in ViewState for future reference 31: ViewState["CurrentTable"] = dt; 32:   33: return dt; 34:   35: } 36:   37: private void BindGridView(DataTable dtSource) { 38: GridView1.DataSource = dtSource; 39: GridView1.DataBind(); 40: } 41:   42: private DataRow InsertRow(DataTable dtSource, string value) { 43: DataRow dr = dtSource.NewRow(); 44: dr["RowNumber"] = value; 45: return dr; 46: } 47: //private DataRow DeleteRow(DataTable dtSource, 48:   49: protected void Page_Load(object sender, EventArgs e) { 50: if (!IsPostBack) { 51: BindGridView(FillData()); 52: } 53: } 54:   55: protected void LinkButton1_Click(object sender, EventArgs e) { 56: LinkButton lb = (LinkButton)sender; 57: GridViewRow row = (GridViewRow)lb.NamingContainer; 58: DataTable dtCurrentData = (DataTable)ViewState["CurrentTable"]; 59: if (lb.Text == "Insert") { 60: //Insert new row below the selected row 61: dtCurrentData.Rows.InsertAt(InsertRow(dtCurrentData, row.Cells[0].Text + "-sub"), row.RowIndex + 1); 62:   63: } 64: else { 65: //Delete selected sub row 66: dtCurrentData.Rows.RemoveAt(row.RowIndex); 67: } 68:   69: BindGridView(dtCurrentData); 70: ViewState["CurrentTable"] = dtCurrentData; 71: } 72:   73: protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) { 74: if (e.Row.RowType == DataControlRowType.DataRow) { 75: if (e.Row.Cells[0].Text.Contains("-sub")) { 76: ((LinkButton)e.Row.FindControl("LinkButton1")).Text = "Delete"; 77: } 78: } 79: }   As you can see the code above is pretty straight forward and self explainatory but just to give you a short explaination the code above is composed of three (3) private methods which are the FillData(), BindGridView and InsertRow(). The FillData() method is a method that returns a DataTable and basically creates a dummy data in the DataTable to be used as the GridView DataSource. You can replace the code in that method if you want to use actual data from database but for the purpose of this example I just fill the DataTable with a dummy data on it. The BindGridVew is a method that handles the actual binding of GridVew. The InsertRow() is a method that returns a DataRow. This method handles the insertion of the sub row. Now in the LinkButton OnClick event, we casted the sender to a LinkButton to determine the specific object that fires up the event and get the row values. We then reference the Data from ViewState to get the current data that is being used in the GridView. If the LinkButton text is "Insert" then we will insert new row to the DataSource ( in this case the DataTable) based on the rowIndex if not then Delete the sub row that was added. Here are some screen shots of the output below: On initial load:   After inserting a sub row:   That's it! I hope someone find this post useful!   Technorati Tags: ASP.NET,C#,GridView

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  • Where are my sub templates?

    - by Tim Dexter
    This one is for standalone/BIEE uses of Publisher. All the ERP/CRM/HCM folks are already catered for and can tuck into a nut cutlet and arugala salad. Sorry, I have just watched Food Inc and even if only half of it is true; Im still on a crusade in my house against mass produced food. Wake up World! If you have ventured into the world of sub templating, you'll be reaping some development benefit. In terms of shared report components and calculations they are very useful. Just exporting all of your report headers and footers to a single sub template can potentially save you hours and hours of work and make you look like a star. If someone in management gets it into their head that they would like Comic San Serif font rather than Arial in their report headers, its a 10 min job rather than 100 hours! What about the rest of the report content? I hear you cry. Its coming in 11g, full master template support. Your management wants bright blue borders with yellow backgrounds for all the tables in your reports, 5 minute job! Getting back to sub templates and my comment about all the ERP/CRM/HCM folks be catered for. In the standalone release there is no out of the box directory for you to drop your sub templates. Dropping them into the main report directory would make sense but they are not accessible there via a URL. An oversight on our part and something that will be addressed in 11g. Sub templates are now a first class citizen in the world of BIP, you can upload them and BIP will know what to do with them. But what do you do right now? The easiest place to put them where BIP can 'see' them is to create a directory under the xmlpserver install directory in the J2EE container e.g. $J2EE_HOME/xmlpserver/xmlpserver/subtemplates You can call it whatever you want but when the server is started up, that directory is accessible via a URL i.e. http://tdexter:9704/xmlpserver/subtemplates/mysub.rtf. You can therefore put it into the top of your main templates and call the sub template. <?import: http://tdexter:9704/xmlpserver/subtemplates/mysub.rtf?> Of course, you can drop them anywhere you want, they just need to be in a web server mountable directory. Enjoy the arugala!

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  • Sorting Algorithms

    - by MarkPearl
    General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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  • Visual C#, Large Arrays, and LOH Fragmentation. What is the accepted convention?

    - by Gorchestopher H
    I have an other active question HERE regarding some hopeless memory issues that possibly involve LOH Fragmentation among possibly other unknowns. What my question now is, what is the accepted way of doing things? If my app needs to be done in Visual C#, and needs to deal with large arrays to the tune of int[4000000], how can I not be doomed by the garbage collector's refusal to deal with the LOH? It would seem that I am forced to make any large arrays global, and never use the word "new" around any of them. So, I'm left with ungraceful global arrays with "maxindex" variables instead of neatly sized arrays that get passed around by functions. I've always been told that this was bad practice. What alternative is there? Is there some kind of function to the tune of System.GC.CollectLOH("Seriously") ? Are there possibly some way to outsource garbage collection to something other than System.GC? Anyway, what are the generally accepted rules for dealing with large (85Kb) variables?

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  • 2D Array of 2D Arrays (C# / XNA) [on hold]

    - by Lemoncreme
    I want to create a 2D array that contains many other 2D arrays. The problem is I'm not quite sure what I'm doing but this is the initialization code I have: int[,][,] chunk = new int[64, 64][32, 32]; For some reason Visual Studio doesn't like this and says that it's and 'invalid rank specifier'. Also, I'm not sure how to use the nested arrays once I've declared them... Some help and some insight, please?

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  • Proper Usage of Arrays and Functions [closed]

    - by Ssegawa Victor
    Can some one help me write a C code that solves the following problem. PROBLEM Consider the faculty registrar who has to process results for 1st year 1st semester students. Students offer five courses CSC 1100, CSK 1101, CSC 1104, CSC 1105 and CSC 1106. The courses have credit units 4,4,4,3 and 3 respectively. Lecturers provide course work and exam marks. For each course, course work constitutes 40% of the final mark while the exam constitutes 60% of the final mark. The role of the registrar is to Compute the final mark for each student for each course. The final mark must be a whole number Compute the grade and grade point of the students for each course they offered. According to senate regulations, grades and grade points are awarded to final marks according to the following criteria Range Grade Grade Point 90 – 100 A+ 5.0 80 – 89 A 5.0 75 – 79 B+ 4.5 70 – 74 B 4.0 65 – 69 C+ 3.5 60 – 64 C 3.0 55 – 59 D+ 2.5 50 – 54 D 2.0 45 – 49 E 1.5 40 – 44 E- 1.0 0 – 39 F 0.0 Put a comment ‘Retake’ to a student for every course where the Grade Point is less than 2.0 Compute the cumulative grade point average CGPA for each student. The senate formula for CGPA is GGPA =(?_(i=1)^(i=N)¦?CU _i×GP _i ?)/(?_(i=1)^(i=N)¦CU i) Put a comment “Progress” for any student whose GGPA is greater than 2 and “Stay Put” on a student whose CGPA is less than 2 You are required to create a c program that considers a class of 25 students and: 1.Initializes an array ‘student’ which stores student names 2.Initializes arrays for course work and exam for each course. ‘cw_csc_1100’ and ‘ex_csc_1100’ store course work and exam marks (respectively) for CSC 1100. The same approach is considered for all other courses 3.Initializes the coursework and exam marks arrays with marks between 0 and 99 4.Write appropriate functions that will generate the final marks, generate grades, generate grade points, generate cumulative grade points, generate comments for students and comments for courses per student 5.Create appropriate arrays for final marks and insert the data there using the appropriate functions 6.Without having to create any extra arrays, use the functions created to generate a report per student that looks like the one bellow. Student Name: Ngubiri Course Unit Final mark Grade Grade Point Course Comment CSC 1100 43 E- 1.0 Retake CSK 1101 50 D 2.0 CSC 1104 59 D+ 2.5 CSC 1105 70 B 4.0 CSC 1106 65 C+ 3.5 CGPA 2.47 Overall Comment Progress NB It is advisable that the indices are used to identify the owners. Eg if student[x] is John, then cs_csc_100[x] should be a mark for John since the index is the same

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  • Sub-Zero’s Glasses Get Broken [Video]

    - by Asian Angel
    Sub-Zero and Liu Kang are in the middle of a serious round of combat when an unexpected problem occurs. Sub-Zero apparently decided to keep his glasses in his pocket and one bicycle kick later they are history. Will this be the only problem to occur during the fight or are things going to get worse? Sub-Zero’s Glasses Are Broken [Dorkly] HTG Explains: What Is Windows RT and What Does It Mean To Me? HTG Explains: How Windows 8′s Secure Boot Feature Works & What It Means for Linux Hack Your Kindle for Easy Font Customization

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