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  • vector <T *> destructor

    - by Daniel.Z
    I have a class defined like: Class A { public: int num; A *parent; vector<A *> children; ... // constructor without parameters A(void) { this->num = 3; this->parent = 0; for (int i=0;i<num;++i) children.push_back(new A(this,num-1)); } // constructor with parameters A(A *a,int n) { this->num = n; this->children->parent = a; for (int i=0;i<num;++i) this->children.push_back(new A(this,this->num-1)); } }; now, the constructor works fine. there are some problem with destructor. currently, the destructor is defined as: A::~A(void) { if (this->parent!=0) this->parent = 0; for (int i=0;i<(int)children.size();++i) this->children[i]->~A(); vector <A *> ().swap(this->children); } but every time when I debug it, it will break at: void deallocate(pointer _Ptr, size_type) { // deallocate object at _Ptr, ignore size ::operator delete(_Ptr); } it looks like I cannot delete the pointer in the vector of this-children, is there any way that I can de-construct the class successfully?

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  • Segmentation Fault?

    - by user336808
    Hello, when I run this program while inputting a number greater than 46348, I get a segmentation fault. For any values below it, the program works perfectly. I am using CodeBlocks 8.02 on Ubuntu 10.04 64-bit. The code is as follows: int main() { int number = 46348; vector<bool> sieve(number+1,false); vector<int> primes; sieve[0] = true; sieve[1] = true; for(int i = 2; i <= number; i++) { if(sieve[i]==false) { primes.push_back(i); int temp = i*i; while(temp <= number) { sieve[temp] = true; temp = temp + i; } } } for(int i = 0; i < primes.size(); i++) cout << primes[i] << " "; return 0; }

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  • Processing velocity-vectors during collision as neatly as possible

    - by DevEight
    Hello. I'm trying to create a good way to handle all possible collisions between two objects. Typically one will be moving and hitting the other, and should then "bounce" away. What I've done so far (I'm creating a typical game where you have a board and bounce a ball at bricks) is to check if the rectangles intersect and if they do, invert the Y-velocity. This is a really ugly and temporary solution that won't work in the long haul and since this is kind of processing is very common in games I'd really like to find a great way of doing this for future projects aswell. Any links or helpful info is appreciated. Below is what my collision-handling function looks like right now. protected void collision() { #region Boundaries if (bal.position.X + bal.velocity.X >= viewportRect.Width || bal.position.X + bal.velocity.X <= 0) { bal.velocity.X *= -1; } if (bal.position.Y + bal.velocity.Y <= 0) { bal.velocity.Y *= -1; } #endregion bal.rect = new Rectangle((int)bal.position.X+(int)bal.velocity.X-bal.sprite.Width/2, (int)bal.position.Y-bal.sprite.Height/2+(int)bal.velocity.Y, bal.sprite.Width, bal.sprite.Height); player.rect = new Rectangle((int)player.position.X-player.sprite.Width/2, (int)player.position.Y-player.sprite.Height/2, player.sprite.Width, player.sprite.Height); if (bal.rect.Intersects(player.rect)) { bal.position.Y = player.position.Y - player.sprite.Height / 2 - bal.sprite.Height / 2; if (player.position.X != player.prevPos.X) { bal.velocity.X -= (player.prevPos.X - player.position.X) / 2; } bal.velocity.Y *= -1; } foreach (Brick b in brickArray.list) { b.rect.X = Convert.ToInt32(b.position.X-b.sprite.Width/2); b.rect.Y = Convert.ToInt32(b.position.Y-b.sprite.Height/2); if (bal.rect.Intersects(b.rect)) { b.recieveHit(); bal.velocity.Y *= -1; } } brickArray.removeDead(); }

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  • how to Solve the "Digg" problem in MongoDB

    - by user193116
    A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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  • JOIN (SELECT DISTINCT [..] substitute

    - by FRKT
    Hello, I'd like to find a substitute for using SELECT DISTINCT in a derived table. Let's say I have three tables: CREATE TABLE `trades` ( `tradeID` int(11) unsigned NOT NULL AUTO_INCREMENT, `employeeID` int(11) unsigned NOT NULL, `corporationID` int(11) unsigned NOT NULL, `profit` int(11) NOT NULL, KEY `tradeID` (`tradeID`), KEY `employeeID` (`employeeID`), KEY `corporationID` (`corporationID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 CREATE TABLE `corporations` ( `corporationID` int(11) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`corporationID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 CREATE TABLE `employees` ( `employeeID` int(11) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`employeeID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 Let's say I'd like to find out how much profit a specific employee has generated. Simple: SELECT SUM(profit) FROM trades JOIN employees ON trades.employeeID = employees.employeeID AND employees.employeeID = 1; It gets trickier if I'd like to query how much revenue a specific corporation has, however. I cannot simply replicate the aforementioned query, because two or more employees from the same company might be involved in the same trade. This query should do the trick: SELECT SUM(profit) FROM trades JOIN (SELECT DISTINCT tradeID FROM trades WHERE trades.corporationID = 1) ... unfortunately, DISTINCT JOINs seem crazy ineffective. Is there any alternative I can use to determine how much revenue a corporation has, taking into account that a corporation might be listed several times with the same tradeID?

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  • How to use two parameters pointing to the same structure in one function ?

    - by ZaZu
    Hey guys, I have my code below that consits of a structure, a main, and a function. The function is supposed to display two parameters that have certain values, both of which point to the same structure. The problem I dont know how to add the SECOND parameter onto the following code : #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; for(i=0;i<5;i++){ printf("%f,(*test).what[z][x]); } return 0; } I need to add a new parameter test_2 there (IN THE SAME FUNCTION) using this code : for(i=0;i<5;i++){ printf("%f,(*test_2).what[z][x]); How does int trialtest(trial *test) changes ? and how does it change in main ? I know that I should declare test_2 as well, like this : trial test,test_2; But what about passing the address in the function ? I do not need to edit it right ? trialtest(&test); --- This will remain the same ? So please, tell me how would I use test_2 as a parameter pointing to the same structure as test, both in the same function.. Thank you !! Please tell me if you need more clarification

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  • get and set for class in model - MVC 2 asp.net

    - by bergin
    Hi there, I want to improve the program so it has a proper constructor but also works with the models environment of MVC. I currently have: public void recordDocument(int order_id, string filename, string physical_path, string slug, int bytes) { ArchiveDocument doc = new ArchiveDocument(); doc.order_id = order_id; doc.filename = filename; doc.physical_path = physical_path; doc.slug = slug; doc.bytes = bytes; db.ArchiveDocuments.InsertOnSubmit(doc); } This obviously should be a constructor and should change to the leaner: public void recordDocument(ArchiveDocument doc) { db.ArchiveDocuments.InsertOnSubmit(doc); } with a get & set somewhere else - not sure of the syntax - do I create a partial class? so: creating in the somewhere repository - ArchiveDocument doc = new ArchiveDocument(order_id, idTaggedFilename, physical_path, slug, bytes); and then: namespace ordering.Models { public partial class ArchiveDocument { int order_id, string filename, string physical_path, string slug, int bytes; public archiveDocument(int order_id, string filename, string physical_path, string slug, int bytes){ this.order_id = order_id; etc } } How should I alter the code?

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  • static variable lose its value

    - by user542719
    I have helper class with this static variable that is used for passing data between two classes. public class Helper{ public static String paramDriveMod;//this is the static variable in first calss } this variable is used in following second class mathod public void USB_HandleMessage(char []USB_RXBuffer){ int type=USB_RXBuffer[2]; MESSAGES ms=MESSAGES.values()[type]; switch(ms) { case READ_PARAMETER_VALUE: // read parameter values switch(prm){ case PARAMETER_DRIVE_MODE: // paramet drive mode Helper.paramDriveMod =(Integer.toString(((USB_RXBuffer[4]<< 8)&0xff00))); System.out.println(Helper.paramDriveMod+"drive mode is selectd ");//here it shows the value that I need. ..........}}//let say end switch and method and the following is an third class method use the above class method public void buttonSwitch(int value) throws InterruptedException{ boolean bool=true; int c=0; int delay=(int) Math.random(); while(bool){ int param=3; PARAMETERS prm=PARAMETERS.values()[param]; switch(value){ case 0: value=1; while(c<5){ Thread.sleep(delay); protocol.onSending(3,prm.PARAMETER_DRIVE_MODE.ordinal(),dataToRead,dataToRead.length);//read drive mode System.out.println(Helper.paramDriveMod+" drive mode is ..........in wile loop");//here it shows null value }}//let say end switch and method what is the reason that this variable lose its value?

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  • BUG - ProteaAudio with Lua does not work

    - by Stackfan
    Any idea why i cant use or cant build in Lua the ProTeaAudio ? 1) Exist [root@example ~]# yum install lua-devel Loaded plugins: presto, refresh-packagekit Setting up Install Process Package lua-devel-5.1.4-4.fc12.i686 already installed and latest version Nothing to do 2) get failed to build the RtAudio [sun@example proteaAudio_src_090204]$ make g++ -O2 -Wall -DHAVE_GETTIMEOFDAY -D__LINUX_ALSA__ -Irtaudio -Irtaudio/include -I../lua/src -I../archive/baseCode/include -c rtaudio/RtAudio.cpp -o rtaudio/RtAudio.o rtaudio/RtAudio.cpp:365: error: no ‘unsigned int RtApi::getStreamSampleRate()’ member function declared in class ‘RtApi’ rtaudio/RtAudio.cpp: In member function ‘virtual bool RtApiAlsa::probeDeviceOpen(unsigned int, RtApi::StreamMode, unsigned int, unsigned int, unsigned int, RtAudioFormat, unsigned int*, RtAudio::StreamOptions*)’: rtaudio/RtAudio.cpp:5835: error: ‘RTAUDIO_SCHEDULE_REALTIME’ was not declared in this scope rtaudio/RtAudio.cpp:5837: error: ‘struct RtAudio::StreamOptions’ has no member named ‘priority’ make: *** [rtaudio/RtAudio.o] Error 1 [sun@example proteaAudio_src_090204]$ Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio > require("proAudioRt"); stdin:1: module 'proAudioRt' not found: no field package.preload['proAudioRt'] no file './proAudioRt.lua' no file '/usr/share/lua/5.1/proAudioRt.lua' no file '/usr/share/lua/5.1/proAudioRt/init.lua' no file '/usr/lib/lua/5.1/proAudioRt.lua' no file '/usr/lib/lua/5.1/proAudioRt/init.lua' no file './proAudioRt.so' no file '/usr/lib/lua/5.1/proAudioRt.so' no file '/usr/lib/lua/5.1/loadall.so' stack traceback: [C]: in function 'require' stdin:1: in main chunk [C]: ?

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  • How to declare array of 2D array pointers and access them?

    - by vikramtheone
    Hi Guys, How can I declare an 2D array of 2D Pointers? And later access the individual array elements of the 2D arrays. Is my approach correct? main() { int i, j; int **array[10][10]; int **ptr = NULL; for(i=0;i<10;i++) { for(j=0j<10;j++) { alloc_2D(&ptr, 10, 10); array[i][j] = ptr; } } //After I do this, how can I access the individual 2D array //and then the individual elements of the 2D arrays? } void alloc_2D(float ***memory, unsigned int rows, unsigned int cols) { float **ptr; *memory = NULL; ptr = malloc(rows * sizeof(float*)); if(ptr == NULL) { status = ERROR; printf("\nERROR: Memory allocation failed!"); } else { int i; for(i = 0; i< rows; i++) { ptr[i] = malloc(cols * sizeof(float)); if(ptr[i]==NULL) { status = ERROR; printf("\nERROR: Memory allocation failed!"); } } } *memory = ptr; }

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  • Why do I get errors when using unsigned integers in an expression with C++?

    - by neuviemeporte
    Given the following piece of (pseudo-C++) code: float x=100, a=0.1; unsigned int height = 63, width = 63; unsigned int hw=31; for (int row=0; row < height; ++row) { for (int col=0; col < width; ++col) { float foo = x + col - hw + a * (col - hw); cout << foo << " "; } cout << endl; } The values of foo are screwed up for half of the array, in places where (col - hw) is negative. I figured because col is int and comes first, that this part of the expression is converted to int and becomes negative. Unfortunately, apparently it doesn't, I get an overflow of an unsigned value and I've no idea why. How should I resolve this problem? Use casts for the whole or part of the expression? What type of casts (C-style or static_cast<...)? Is there any overhead to using casts (I need this to work fast!)? EDIT: I changed all my unsigned ints to regular ones, but I'm still wondering why I got that overflow in this situation.

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  • Java HashMap containsKey always false

    - by Dennis
    I have the funny situation, that I store a Coordinate into a HashMap<Coordinate, GUIGameField>. Now, the strange thing about it is, that I have a fragment of code, which should guard, that no coordinate should be used twice. But if I debug this code: if (mapForLevel.containsKey(coord)) { throw new IllegalStateException("This coordinate is already used!"); } else { ...do stuff... } ... the containsKey always returns false, although I stored a coordinate with a hashcode of 9731 into the map and the current coord also has the hashcode 9731. After that, the mapForLevel.entrySet() looks like: (java.util.HashMap$EntrySet) [(270,90)=gui.GUIGameField@29e357, (270,90)=gui.GUIGameField@ca470] What could I have possibly done wrong? I ran out of ideas. Thanks for any help! public class Coordinate { int xCoord; int yCoord; public Coordinate(int x, int y) { ...store params in attributes... } ...getters & setters... @Override public int hashCode() { int hash = 1; hash = hash * 41 + this.xCoord; hash = hash * 31 + this.yCoord; return hash; } }

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  • How to define and use a friend function to a temlate class with the same template?

    - by Narek
    I have written the following code: #include <iostream> using namespace std; template <class T> class AA { T a; public: AA() { a = 7; } friend void print(const AA<T> & z); }; template <class T> void print(const AA<T> & z) { cout<<"Print: "<<z.a<<endl; } void main() { AA<int> a; print<int>(a); } And getting the following error: error C2248: 'AA<T>::a' : cannot access private member declared in class 'AA<T>' 1> with 1> [ 1> T=int 1> ] 1> c:\users\narek\documents\visual studio 2008\projects\aaa\aaa\a.cpp(7) : see declaration of 'AA<T>::a' 1> with 1> [ 1> T=int 1> ] 1> c:\users\narek\documents\visual studio 2008\projects\aaa\aaa\a.cpp(30) : see reference to function template instantiation 'void print<int>(const AA<T> &)' being compiled 1> with 1> [ 1> T=int 1> ] What's wrong?

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  • Scratch the screen to display an image in android

    - by user1008497
    i am working on a android project for my assignment. i am trying to make a scratch image application, you know it's like we scratch the screen to get rid the blocking layer to display the image. but the problem is i don't know where to start. i have searching in stackoverflow's questions that related to this but that's not help. from my search there, i found a clue for this project is using Bitmap.getPixel(int x, int y). so, in my thought i have to get pixel from bitmap and paint it to canvas. but i don't know how to implement it? or anyone has a better method for this? Could anyone please help me? Any tutorials on this kind of thing or related topics? Thanks in advance! here's my sample code: @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); tw = w; th = h; eraseableBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); mCanvas = new Canvas(eraseableBitmap); Bitmap muteableBitmap = Bitmap.createBitmap(eraseableBitmap.getWidth(), eraseableBitmap.getHeight(), Bitmap.Config.ARGB_8888); } @Override public boolean onTouchEvent(MotionEvent event) { static_x = event.getX(); static_y = event.getY(); if (event.getAction() == MotionEvent.ACTION_DOWN) { touch_start(static_x, static_y); } if (event.getAction() == MotionEvent.ACTION_MOVE) { touch_move(static_x, static_y); } if (event.getAction() == MotionEvent.ACTION_UP) { touch_up(); } return true; }

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  • What's the problem with the code below ?

    - by VaioIsBorn
    #include <iostream> #include <vector> using namespace std; int main(void) { int i, s, g; vector<int> a; cin >> s; for(i=1;i<=s;i++) { g = s; if(g<10) a.push_back(g); else { vector<int> temp; while(g > 0) { int k = g % 10; g = g / 10; temp.push_back(g); } for(int j=temp.size();j>0;j--) { a.push_back(temp[j]); } } } cout << a[s-1] << endl; return 0; } What is wrong with the code above ? It doesn't give me the appropriate results. The vector a is supposed to hold the values from 1, 2, 3...up to s such that a = 12345..910111213... and print to output a[s]. Ex if s=15 a=123456789101112131415 and a[15] = 2 . If someone could tell me what's the problem

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  • Deleting elements from stl set while iterating through it does not invalidate the iterators.

    - by pedromanoel
    I need to go through a set and remove elements that meet a predefined criteria. This is the test code I wrote: #include <set> #include <algorithm> void printElement(int value) { std::cout << value << " "; } int main() { int initNum[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; std::set<int> numbers(initNum, initNum + 10); // print '0 1 2 3 4 5 6 7 8 9' std::for_each(numbers.begin(), numbers.end(), printElement); std::set<int>::iterator it = numbers.begin(); // iterate through the set and erase all even numbers for (; it != numbers.end(); ++it) { int n = *it; if (n % 2 == 0) { // wouldn't invalidate the iterator? numbers.erase(it); } } // print '1 3 5 7 9' std::for_each(numbers.begin(), numbers.end(), printElement); return 0; } At first, I thought that erasing an element from the set while iterating through it would invalidate the iterator, and the increment at the for loop would have undefined behavior. Even though, I executed this test code and all went well, and I can't explain why. My question: Is this the defined behavior for std sets or is this implementation specific? I am using gcc 4.3.3 on ubuntu 10.04 (32-bit version), by the way. Thanks!

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  • In which year was the date the same as the original year?

    - by Marta
    It's my first question on this site, but I always found this site really useful. What I mean with my question is: you ask the person to give a date (eg. Fill in a date [dd-mm-yyyy]: 16-10-2013) you than have to ask an interval between 2 years (eg. Give an interval [yyyy-yyyy]:1800-2000) When the program runs, it has to show what day of the week the given date is. In this case it was a Wednesday. Than the program has to look in which year, in between the interval, the date 16 October also fell on a Wednesday. So in the end it has to look something like this: Fill in a date: [dd-mm-yyyy]: 16-10-2013 Give an interval [yyyy-yyyy]: 1900-2000 16 October was a wednesday in the following years: 1905 1911 1916 1922 1933 1939 1944 1950 1961 1967 1972 1978 1989 1995 2000 The full date is Wednesday 16 October, 2013 The small (or biggest) problem is, I am not allowed to use the DATE.function in java. If someone can help me with the second part I would be really really happy, cause I have no idea how I am supposed to do this To find out what day of the week the given date falls, I use the Zeller Congruence class Day { Date date; //To grab the month and year form the Date class int day; final static String[] DAYS_OF_WEEK = { "Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" }; public void dayWeekInterval{ //code to grab the interval from interval Class, and doing stuff here } public void dayOfTheWeek { int m = date.getMonth(); int y = date.getYear(); if (m < 3) { m += 12; y -= 1; } int k = y % 100; int j = y / 100; int day = ((q + (((m + 1) * 26) / 10) + k + (k / 4) + (j / 4)) + (5 * j)) % 7; return day; } public string ToString(){ return "" + DAYS_OF_WEEK[day] + day; } }

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  • C# Finding 2 positions 1-dimArray

    - by Chris
    Hello, In a method i am calculating the longest row of elements. The 1-dim array is filled up with random values (0 or 1). The method looks up the longest row (being 0 or 1, whatever is the longest). Meaning in for example: 1110100 --> the longest row would be 3 (3 * 1) 0110000 --> the longest row would be 4 (4 * 0) My problem is i am trying to perform some type of linear search to show the position of the row in the array. The first example has the longest row of 3 elements (3 times 1). For 1110100 the position in the array would be 0 - 2 (index) For 0110000 the position in the array would be 3 - 6 (index) I have been trying with foreaches, for loops etc..but i cannot seem to get the proper indexes of both. Cannot seem to display both positions properly. For the first example the correct output wouldbe: The largest row of same elements of the array consists of 3 elements on the position 0 - 2. The longest row of elements gets of same elements get calculated as the following: public int BerekenDeelrij (int [] table) ( int count = 0; final int value = 0; int largest = 0; foreach (int value in table) ( if (value == last value) counter + +; else ( largest = Math.Max largest (largest, counter); final value = value count = 1; ) ) Math.Max return (largest, counter); ) Best Regards.

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  • Need help with if else statement

    - by Michael Quiles
    I'm trying to do an else statement that would tell the user that the game ended in a draw (tic tac toe game). I got it where it works if played and there's a winner it will show another form declaring the winner through an if statement but I cant figure out the its a draw portion. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows.Forms; using System.Drawing; namespace MyGame { public class Result1 { static private int[,] Winners = new int[,] { // main gameplay Ex: if x is on 0,1,2 x is the winner {0,1,2}, {3,4,5}, {6,7,8}, {0,3,6}, {1,4,7}, {2,5,8}, {0,4,8}, {2,4,6}, }; static public bool CheckWinner(Button[] myControls) { //bolean statement to check for the winner bool gameOver = false; for (int i = 0; i < 8; i++) { int a = Winners[i, 0]; int b = Winners[i, 1]; int c = Winners[i, 2]; Button b1 = myControls[a], b2 = myControls[b], b3 = myControls[c]; if (b1.Text == "" || b2.Text == "" || b3.Text == "") continue; if (b1.Text == b2.Text && b2.Text == b3.Text) { b1.BackColor = b2.BackColor = b3.BackColor = Color.LightCoral; b1.Font = b2.Font = b3.Font = new System.Drawing.Font("Microsoft Sans Serif", 32F, System.Drawing.FontStyle.Italic & System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0))); gameOver = true; xWinnerForm xWinnerForm = new xWinnerForm(); xWinnerForm.ShowDialog(); //only works with show not showDialog method gets overloaded (b1.Text + " is the Winner"); to get around this I added and image showing the last player } //else statement here for draw what code would I put in? } return gameOver; } } }

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  • Uniform grid Rows and Columns

    - by Carlo
    I'm trying to make a grid based on a UniformGrid to show the coordinates of each cell, and I want to show the values on the X and Y axes like so: _A_ _B_ _C_ _D_ 1 |___|___|___|___| 2 |___|___|___|___| 3 |___|___|___|___| 4 |___|___|___|___| Anyway, in order to do that I need to know the number of columns and rows in the Uniform grid, and I tried overriding the 3 most basic methods where the arrangement / drawing happens, but the columns and rows in there are 0, even though I have some controls in my grid. What method can I override so my Cartesian grid knows how many columns and rows it has? C#: public class CartesianGrid : UniformGrid { protected override Size MeasureOverride(Size constraint) { Size size = base.MeasureOverride(constraint); int computedColumns = this.Columns; // always 0 int computedRows = this.Rows; // always 0 return size; } protected override Size ArrangeOverride(Size arrangeSize) { Size size = base.ArrangeOverride(arrangeSize); int computedColumns = this.Columns; // always 0 int computedRows = this.Rows; // always 0 return size; } protected override void OnRender(DrawingContext dc) { int computedColumns = this.Columns; // always 0 int computedRows = this.Rows; // always 0 base.OnRender(dc); } } XAML: <local:CartesianGrid> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> </local:CartesianGrid> Any help is greatly appreciated. Thanks!

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  • Is this linear search implementation actually useful?

    - by Helper Method
    In Matters Computational I found this interesting linear search implementation (it's actually my Java implementation ;-)): public static int linearSearch(int[] a, int key) { int high = a.length - 1; int tmp = a[high]; // put a sentinel at the end of the array a[high] = key; int i = 0; while (a[i] != key) { i++; } // restore original value a[high] = tmp; if (i == high && key != tmp) { return NOT_CONTAINED; } return i; } It basically uses a sentinel, which is the searched for value, so that you always find the value and don't have to check for array boundaries. The last element is stored in a temp variable, and then the sentinel is placed at the last position. When the value is found (remember, it is always found due to the sentinel), the original element is restored and the index is checked if it represents the last index and is unequal to the searched for value. If that's the case, -1 (NOT_CONTAINED) is returned, otherwise the index. While I found this implementation really clever, I wonder if it is actually useful. For small arrays, it seems to be always slower, and for large arrays it only seems to be faster when the value is not found. Any ideas?

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  • NullReferenceExeption when reading from a file

    - by Whitey
    I need to read a file structured like this: 01000 00030 00500 03000 00020 And put it in an array like this: int[,] iMap = new int[iMapHeight, iMapWidth] { {0, 1, 0, 0, 0}, {0, 0, 0, 3, 0}, {0, 0, 5, 0, 0}, {0, 3, 0, 0, 0}, {0, 0, 0, 2, 0}, }; Hopefully you see what I'm trying to do here. I was confused how to do this so I asked here on SO, but the code I got from it gets this error: Object reference not set to an instance of an object. I'm pretty new to this so I have no idea how to fix it... I only barely know the code: protected void ReadMap(string mapPath) { using (var reader = new StreamReader(mapPath)) { for (int i = 0; i < iMapHeight; i++) { string line = reader.ReadLine(); for (int j = 0; j < iMapWidth; j++) { iMap[i, j] = (int)(line[j] - '0'); } } } } The line I get the error on is this: iMap[i, j] = (int)(line[j] - '0'); Can anyone provide a solution? Thank you. :)

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  • How to fix this simple SQL query?

    - by morpheous
    I have a database with three tables: user_table country_table city_table I want to write ANSI SQL which will allow me to fetch all the user data (i.e. user details including the name of the country of the last school and the name of the city they live in now). The problem I am having is that I have to use a self join, and I am getting slightly confused. The schema is shown below: CREATE TABLE user_table (id int, first_name varchar(16), last_school_country_id int, city_id int); CREATE TABLE country_table (id int, name varchar(32)); CREATE TABLE city_table (id int, country_id int, name varchar(32)); This is the query I have come up with so far, but the results are wrong, and sometimes, the db engine (mySQL), asks me if I want to show all [HUGE NUMBER HERE] results - which makes me suspect that I am unintentionally creating a cartesian product somewhere. Can someone explain what is wrong with this SQL statement, and what I need to do to fix it? SELECT usr.id AS id, usr.first_name, ctry1.name as loc_country_name, ctry2.name as school_country_name, city.name as loc_city_name FROM user_table usr, country_table ctry1, country_table ctry2, city_table city WHERE usr.last_school_country_id=ctry2.id AND usr.city_id=city.id AND city.country_id=ctry1.id AND ctry1.id=ctry2.id;

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  • What's the most trivial function that would benfit from being computed on a GPU?

    - by hanDerPeder
    Hi. I'm just starting out learning OpenCL. I'm trying to get a feel for what performance gains to expect when moving functions/algorithms to the GPU. The most basic kernel given in most tutorials is a kernel that takes two arrays of numbers and sums the value at the corresponding indexes and adds them to a third array, like so: __kernel void add(__global float *a, __global float *b, __global float *answer) { int gid = get_global_id(0); answer[gid] = a[gid] + b[gid]; } __kernel void sub(__global float* n, __global float* answer) { int gid = get_global_id(0); answer[gid] = n[gid] - 2; } __kernel void ranksort(__global const float *a, __global float *answer) { int gid = get_global_id(0); int gSize = get_global_size(0); int x = 0; for(int i = 0; i < gSize; i++){ if(a[gid] > a[i]) x++; } answer[x] = a[gid]; } I am assuming that you could never justify computing this on the GPU, the memory transfer would out weight the time it would take computing this on the CPU by magnitudes (I might be wrong about this, hence this question). What I am wondering is what would be the most trivial example where you would expect significant speedup when using a OpenCL kernel instead of the CPU?

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  • What are the benefits of `while(condition) { //work }` and `do { //work } while(condition)`?

    - by Shaharyar
    I found myself confronted with an interview question where the goal was to write a sorting algorithm that sorts an array of unsorted int values: int[] unsortedArray = { 9, 6, 3, 1, 5, 8, 4, 2, 7, 0 }; Now I googled and found out that there are so many sorting algorithms out there! Finally I could motivate myself to dig into Bubble Sort because it seemed pretty simple to start with. I read the sample code and came to a solution looking like this: static int[] BubbleSort(ref int[] array) { long lastItemLocation = array.Length - 1; int temp; bool swapped; do { swapped = false; for (int itemLocationCounter = 0; itemLocationCounter < lastItemLocation; itemLocationCounter++) { if (array[itemLocationCounter] > array[itemLocationCounter + 1]) { temp = array[itemLocationCounter]; array[itemLocationCounter] = array[itemLocationCounter + 1]; array[itemLocationCounter + 1] = temp; swapped = true; } } } while (swapped); return array; } I clearly see that this is a situation where the do { //work } while(cond) statement is a great help to be and prevents the use of another helper variable. But is this the only case that this is more useful or do you know any other application where this condition has been used?

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