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  • C++ Boolean problem (comparison between two arrays)

    - by Martin
    Hello! I have a problem to do. I already did some part of it, however I stuck and don't know exactly what to do next. The question: " You are given two arrays of ints, named A and B. One contains AMAXELEMENTS and the other contains BMAXELEMENTS. Write a Boolean-valued function that returns true if there is at least one point in A that is the same as a point in B, and false if there is no match between two arrays. " The two arrays are made up by me, I think if I know how to compare two arrays I will be fine, and I will be able to finish my problem. This is what I have so far (I changed AMAXELEMENTS to AMAX, and BMAXELEMENTS to BMAX): #include <iostream> using namespace std; int main(){ const int AMAX=5, BMAX=6; int i; bool c1=true,c2=false; int A[AMAX]={2,4,1,5,9}; int B[BMAX]={9,12,32,43,23,11}; for(i=0;i<BMAX;i++) if (B[i]==A[i]) // <---- I think this part has to look different, but I can't figure it out. cout<<c1<<endl; else cout<< c2<<endl; return 0; }

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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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  • Randomised objects are assigning themselves to more than one array location

    - by Thaddeus Aid
    this.size = 9; this.populationSize = 10; Random rand = new Random(); Integer[][] easy1 = new Integer[size][size]; easy1 = this.initializeEasy1(easy1); this.sudokuArray = new Sudoku[this.populationSize]; for (int i = 0; i < this.sudokuArray.length; i++){ long seed = rand.nextLong(); System.out.println("" + seed); this.sudokuArray[i] = new Sudoku(easy1, this.size, seed); } I am building an evolutionary sudoku solver and I am having a problem where the last Sudoku object is overwriting all the other objects in the array. Where in the code did I mess up? /edit here is the constructor of the class public Sudoku(Integer[][] givensGrid, int s, long seed){ this.size = s; this.givens = givensGrid; this.grid = this.givens.clone(); Random rand = new Random(seed); System.out.println("Random " + rand.nextInt()); // step though each row of the grid for (int i = 0; i < size; i++){ ArrayList<Integer> numbers = new ArrayList<Integer>(); numbers = this.makeNumbers(numbers); // step through each column to find the givens and remove from numbers for (int j = 0; j < size; j++){ if (this.grid[i][j] != 0){ numbers.remove(this.grid[i][j]); } } // go back through the row and assign the numbers randomly for (int j = 0; j < size; j++){ if (this.grid[i][j] == 0){ int r = rand.nextInt(numbers.size()); this.grid[i][j] = numbers.get(r); numbers.remove(r); } } } System.out.println("============="); System.out.println(this.toString()); }

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  • How to find the differences between the values of a specific column based on a key?

    - by Holicreature
    I've two tables as purchase_details and invoice_details and i want to store the inventory/stock of each product from the data of these two tables. structure of purchase_details. 'pid', 'int(10)' 'product_id', 'int(10)' 'quantity', 'float(8,2)' 'amount', 'float(12,2)' 'expiry_date', 'date' structure of purchase_details. 'invoice_id', 'int(10) unsigned' 'product_id', 'int(10) unsigned' 'quantity', 'float(10,2)' 'price', 'float(12,2)' i want to calculate the total quantity of remaining stock (quantity of sum of products from purchase_details - quantity of sum of products from invoice_details). Product_id is would be same for the two tables. how can i proceed?

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  • How to use templated classes as function arguments? (C++)

    - by Keand64
    I have a class declared along the lines of template<int a, int b> class C { public: array[a][b]; } and I want to use it as argument in a function like this: bool DoSomeTests(C &c1, C &c2); but when I compile, it tells me 'use of class template requires template argument list.' I tried template<int a, int b> bool DoSomeTests(C &c1, C &c2); but I get the same error. How can I fix this?

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  • C++ and preprocessor macro gotcha

    - by aaa
    hello. Appologies for yet another gotcha question. Can you figure out what is wrong with the statement below? gcc error states: "type name declared as function returning array". #define MACRO(a) (a)[1] class index { typedef int index_type[2]; index_type& operator[](int i); }; int k = 0; int i = MACRO(index()[k]); ps: is such questions are deemed too annoying, I am going to stop.

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  • operator overloading and inheritance

    - by user168715
    I was given the following code: class FibHeapNode { //... // These all have trivial implementation virtual void operator =(FibHeapNode& RHS); virtual int operator ==(FibHeapNode& RHS); virtual int operator <(FibHeapNode& RHS); }; class Event : public FibHeapNode { // These have nontrivial implementation virtual void operator=(FibHeapNode& RHS); virtual int operator==(FibHeapNode& RHS); virtual int operator<(FibHeapNode& RHS); }; class FibHeap { //... int DecreaseKey(FibHeapNode *theNode, FibHeapNode& NewKey) { FibHeapNode *theParent; // Some code if (theParent != NULL && *theNode < *theParent) { //... } //... return 1; } }; Much of FibHeap's implementation is similar: FibHeapNode pointers are dereferenced and then compared. Why does this code work? (or is it buggy?) I would think that the virtuals here would have no effect: since *theNode and *theParent aren't pointer or reference types, no dynamic dispatch occurs and FibHeapNode::operator< gets called no matter what's written in Event.

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  • Clustered index on frequently changing reference table of one or more foreign keys

    - by Ian
    My specific concern is related to the performance of a clustered index on a reference table that has many rapid inserts and deletes. Table 1 "Collection" collection_pk int (among other fields) Table 2 "Item" item_pk int (among other fields) Reference Table "Collection_Items" collection_pk int, item_pk int (combined primary key) Because the primary key is composed of both pks, a clustered index is created and the data physically ordered in the table according to the combined keys. I have many users creating and deleting collections and adding and removing items to those collections very frequently affecting the "Collection_Items" table, and its clustered index. QUESTION PART: Since the "Collection_Items" table is so dynamic, wouldn't there be a big performance hit on constantly resorting the table rows because of the clustered index ? If yes, what should I do to minimize this ?

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  • Assign the results of a stored procedure into a variable in another stored procedure

    - by RHPT
    The title of this question is a bit misleading, but I couldn't summarize this very well. I have two stored procedures. The first stored procedure (s_proc1) calls a second stored procedure (s_proc2). I want to assign the value returned from s_proc2 to a variable in s_proc1. Currently, I'm calling s_proc2 (inside s_proc1) in this manner: EXEC s_proc2 @SiteID, @count = @PagingCount OUTPUT s_proc2 contains a dynamic query statement (for reasons I will not outline here). CREATE dbo.s_proc2 ( @siteID int, @count int OUTPUT ) AS DECLARE @sSQL nvarchar(100) DECLARE @xCount int SELECT @sSQL = 'SELECT COUNT(ID) FROM Authors' EXEC sp_ExecuteSQL @sSQL, N'@xCount int output', @xCount output SET @count = @xCount RETURN @count Will this result in @PagingCount having the value of @count? I ask because the result I am getting from s_proc1 is wonky. In fact, what I do get is two results. The first being @count, then the result of s_proc1 (which is incorrect). So, it makes me wonder if @PagingCount isn't being set properly. Thank you.

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  • Optimize SQL query (Facebook-like application)

    - by fabriciols
    My application is similar to Facebook, and I'm trying to optimize the query that get user records. The user records are that he as src ou dst. The src is in usermuralentry directly, the dst list are in usermuralentry_user. So, a entry can have one src and many dst. I have those tables: mysql> desc usermuralentry ; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | user_src_id | int(11) | NO | MUL | NULL | | | private | tinyint(1) | NO | | NULL | | | content | longtext | NO | | NULL | | | date | datetime | NO | | NULL | | | last_update | datetime | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ 10 rows in set (0.10 sec) mysql> desc usermuralentry_user ; +-------------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------------+---------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | usermuralentry_id | int(11) | NO | MUL | NULL | | | userinfo_id | int(11) | NO | MUL | NULL | | +-------------------+---------+------+-----+---------+----------------+ 3 rows in set (0.00 sec) And the following query to retrieve information from two users. mysql> explain SELECT * FROM usermuralentry AS a , usermuralentry_user AS b WHERE a.user_src_id IN ( 1, 2 ) OR ( a.id = b.usermuralentry_id AND b.userinfo_id IN ( 1, 2 ) ); +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | 1 | SIMPLE | b | ALL | usermuralentry_id,usermuralentry_user_bcd7114e,usermuralentry_user_6b192ca7 | NULL | NULL | NULL | 147188 | | | 1 | SIMPLE | a | ALL | PRIMARY | NULL | NULL | NULL | 1371289 | Range checked for each record (index map: 0x1) | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ 2 rows in set (0.00 sec) but it is taking A LOT of time... Some tips to optimize? Can the table schema be better in my application?

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  • How to implement iterator as an attribute of a class in Java

    - by de3
    Hi, let's say I have this simple MyArray class, with two simple methods: add, delete and an iterator. In the main method we can see how it is supposed to be used: public class MyArray { int start; int end; int[] arr; myIterator it; public MyArray(){ this.start=0; this.end=0; this.arr=new int[500]; it=new myIterator(); } public void add(int el){ this.arr[this.end]=el; this.end++; } public void delete(){ this.arr[this.start]=0; this.start++; } public static void main(String[] args){ MyArray m=new MyArray(); m.add(3); m.add(299); m.add(19); m.add(27); while(m.it.hasNext()){ System.out.println(m.it.next()); } } And then MyIterator should be implemented somehow: import java.util.Iterator; public class myIterator implements Iterator{ @Override public boolean hasNext() { // TODO Auto-generated method stub return false; } @Override public Object next() { // TODO Auto-generated method stub return null; } @Override public void remove() { // TODO Auto-generated method stub } } MyIterator should iterate arr from MyArray class, from start to end values; both are also attributes of MyArray. So, as MyIterator should use MyArray attributes, how should MyIterator be implemented? Perhaps I can send the current object in the initialization: it=new myIterator(this); But I guess it's not the best soultion. Or maybe MyArray itself should implement Iterator interface? How is this solved?

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  • MYSQL autoincrement a column or just have an integer, difference?

    - by David19801
    Hi, If I have a column, set as primary index, and set as INT. If I don't set it as auto increment and just insert random integers which are unique into it, does that slow down future queries compared to autincrementing? Does it speed things up if I run OPTIMIZE on a table with its primary and only index as INT? (assuming only 2 columns, and second column is just some INT value) (the main worry is the upper limit on the autoincrement as theres lots of adds and deletes in my table)

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  • Mysql query question

    - by brux
    I have 2 tables: Customer: customerid - int, pri-key,auto fname - varchar sname -varchar housenum - varchar street -varchar Items: itemid - int,pri-key,auto type - varchar collectiondate - date releasedate - date customerid - int I need a query which will get me all items that have a releasedate 3 days prior to (and including) the current date. i.e The query should return customerid,fname,sname,street,housenum,type,releasedate for all items which have releasedate within (and including)3 days prior today thanks in advance

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  • Pair equal operator overloading for inserting into set

    - by Petwoip
    I am trying to add a pair<int,int> to a set. If a pair shares the same two values as another in the set, it should not be inserted. Here's my non-working code: typedef std::pair<int, int> PairInt; template<> bool std::operator==(const PairInt& l, const PairInt& r) { return (l.first == r.first && l.second == r.second) || (l.first == r.second && l.second == r.first); } int main() { std::set<PairInt> intSet; intSet.insert(PairInt(1,3)); intSet.insert(PairInt(1,4)); intSet.insert(PairInt(1,4)); intSet.insert(PairInt(4,1)); } At the moment, the (4,1) pair gets added even though there is already a (1,4) pair. The final contents of the set are: (1 3) (1 4) (4 1) and I want it to be (1 3) (1 4) I've tried putting breakpoints in the overloaded method, but they never get reached. What have I done wrong?

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  • Regular Expression to parse SQL Structure

    - by user351429
    I am trying to parse the MySQL data types returned by "DESCRIBE [TABLE]". It returns strings like: int(11) float varchar(200) int(11) unsigned float(6,2) I've tried to do the job using regular expressions but it's not working. PHP CODE: $string = "int(11) numeric"; $regex = '/(\w+)\s*(\w+)/'; var_dump( preg_split($regex, $string) );

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  • Why is my custom view not appearing?

    - by user351469
    When I comment out setContentView(boardView); in my Game.java my custom view in BoardView works fine and displays everything nicely... but onSizeChanged never gets called in BoardView.java... so I can't read the device width and height at runtime. If I leave setContentView uncommented onSizeChanged works... but the screen is blank! I want to be able to read the screen width and height at runtime and set the sizes of my ImageViews at creation so they are the optimal size. public class Game extends Activity implements OnClickListener{ private BoardView boardView; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); boardView = new BoardView(this); setContentView(boardView); // when this line disabled, it looks ok boardView.requestFocus(); } public class BoardView extends View { private final Game game; private float width; // width of one unit private float height; // height of one unit public BoardView(Context context){ super(context); this.game = (Game)context; setFocusable(true); setFocusableInTouchMode(true); LinearLayout maincontainer = new LinearLayout(game); maincontainer.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT)); maincontainer.setGravity(Gravity.CENTER); maincontainer.setOrientation(LinearLayout.VERTICAL); maincontainer.setBackgroundColor(Color.BLACK); LinearLayout innercontainer = new LinearLayout(game); innercontainer.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT)); innercontainer.setGravity(Gravity.CENTER); innercontainer.setOrientation(LinearLayout.HORIZONTAL); // declare a new table TableLayout layout = new TableLayout(game); layout.setLayoutParams(new TableLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT)); // build a grid of ImageViews in a TableLayout for (int f=1; f<=7; f++) { TableRow tr = new TableRow(game); for (int c=1; c<=7; c++) { ImageView b = new ImageView(game); b.setImageResource(R.drawable.neworb); b.setOnClickListener(game); tr.addView(b, 30,30); // I'd like to not use fixed values here } // for layout.addView(tr); } // for innercontainer.addView(layout); maincontainer.addView(innercontainer); game.setContentView(maincontainer); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh){ width = w/9f; height = width; super.onSizeChanged(w, h, oldw, oldh); } }

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  • Simple loop, which one I would get more performance and which one is recommended? defining a variable inside a loop or outside of it?

    - by Grego
    Variable outside of the loop int number = 0; for(int i = 0; i < 10000; i++){ number = 3 * i; printf("%d",number); } or Variable inside of the loop for(int i = 0; i < 10000; i++){ int number = 3 * i; printf("%d",number); } Which one is recommended and which one is better in performance? Edit: This is just an example to exhibit what I mean, All I wanna know is if defining a variable inside a loop and outside a loop means the same thing , or there's a difference.

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  • Code Review: CLR RegexSubstring

    - by OMG Ponies
    Could this be better? .NET 2.0 compatibility for SQL Server 2005: public static SqlString RegexSubstring(SqlString regexpattern, SqlString sourcetext, SqlInt32 start_position) { SqlString result = null; if (!regexpattern.IsNull && !sourcetext.IsNull && !start_position.IsNull) { int start_location = (int)start_position >= 0 ? (int)start_position : 0; Regex RegexInstance = new Regex(regexpattern.ToString()); result = new SqlString(RegexInstance.Match(sourcetext.ToString(), (int)start_position).Value); } return result; }

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  • Java - What's the most efficient way of removing a set of elements from an Array[]

    - by fraido
    I've something like this Object[] myObjects = ...(initialized in some way)... int[] elemToRemove = new int[]{3,4,6,8,...} What's the most efficient way of removing the elements of index position 3,4,6,8... from myObjects ? I'd like to implement an efficient Utility method with a signature like public Object[] removeElements(Object[] object, int[] elementsToRemove) {...} The Object[] that is returned should be a new Object of size myObjects.length - elemToRemove.length

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  • C++ reference variable again!!!

    - by kumar_m_kiran
    Hi All, I think most would be surprised about the topic again, However I am referring to a book "C++ Common Knowledge: Essential Intermediate Programming" written by "Stephen C. Dewhurst". In the book, he quotes a particular sentence (in section under Item 5. References Are Aliases, Not Pointers), which is as below A reference is an alias for an object that already exists prior to the initialization of the reference. Once a reference is initialized to refer to a particular object, it cannot later be made to refer to a different object; a reference is bound to its initializer for its whole lifetime Can anyone please explain the context of "cannot later be made to refer to a different object" Below code works for me, #include <iostream> using namespace std; int main(int argc, char *argv[]) { int i = 100; int& ref = i; cout<<ref<<endl; int k = 2000; ref = k; cout<<ref<<endl; return 0; } Here I am referring the variable ref to both i and j variable. And the code works perfectly fine. Am I missing something? I have used SUSE10 64bit linux for testing my sample program. Thanks for your input in advance.

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  • Performance implications of using a variable versus a magic number

    - by Nathan
    I'm often confused by this. I've always been taught to name numbers I use often using variables or constants, but if it reduces the efficiency of the program, should I still do it? Heres an example: private int CenterText(Font font, PrintPageEventArgs e, string text) { int recieptCenter = 125; int stringLength = Convert.ToInt32(e.Graphics.MeasureString(text, font)); return recieptCenter - stringLength / 2; } The above code is using named variables, but runs slower then this code: private int CenterText(Font font, PrintPageEventArgs e, string text) { return 125 - Convert.ToInt32(e.Graphics.MeasureString(text, font) / 2); } In this example, the difference in execution time is minimal, but what about in larger blocks of code?

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