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  • Java - How to declare table[i][j] elements as instance variables?

    - by JDelage
    All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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  • Issue while saving image using savefiledialog

    - by user1097772
    I'm using savefiledialog to save an image. Canvas is picturebox and the loaded image is bitmap. When I try to save it the file is created but somehow corrupted. Cause when I try againt load the image or show in different viewer it doesn't work - I mean the saved file is corrupted. There is an method for saving image. private void saveFileDialog1_FileOk(object sender, CancelEventArgs e) { System.IO.FileStream fs = (System.IO.FileStream)saveFileDialog1.OpenFile(); try { switch (saveFileDialog1.FilterIndex) { case 1: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Bmp); break; case 2: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Jpeg); break; case 3: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Png); break; case 4: canvas.Image.Save(saveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Tiff); break; } } catch (Exception ex) { System.Console.WriteLine("Exception " + ex); } I should also mention the property Filter. saveFileDialog1.Filter has value: bmp (*.bmp)|*.bmp|jpeg (*.jpeg)|*.jpeg|png (*.png)|*.png|tiff (*.tiff)|*.tiff

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  • Optimal sorting algorithm with modified cost... [closed]

    - by David
    The numbers are in a list that is not sorted and supports only one type of operation. The operation is defined as follows: Given a position i and a position j the operation moves the number at position i to position j without altering the relative order of the other numbers. If i j, the positions of the numbers between positions j and i - 1 increment by 1, otherwise if i < j the positions of the numbers between positions i+1 and j decreases by 1. This operation requires i steps to find a number to move and j steps to locate the position to which you want to move it. Then the number of steps required to move a number of position i to position j is i+j. Design an algorithm that given a list of numbers, determine the optimal(in terms of cost) sequence of moves to rearrange the sequence.

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  • Finding the largest subtree in a BST

    - by rakeshr
    Given a binary tree, I want to find out the largest subtree which is a BST in it. Naive approach: I have a naive approach in mind where I visit every node of the tree and pass this node to a isBST function. I will also keep track of the number of nodes in a sub-tree if it is a BST. Is there a better approach than this ?

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  • c program for this quesion

    - by sashi
    suppose that a disk drive has 5000 cylinders, numbered 0 to 4999. the drive is currently serving a request at cylinder 143 and the previous request was at cylinder 125. the ueue of pending requests in the given order is 86,1470,913,17774,948,1509,1022,1750,130. write a 'c' program for finding the total distance in cylinders that the disk arm moves to satisfy all the pending reuests from the current heads position, using SSTF scheduling algorith. seek time is the time for the disk arm to move the head to the cylider containing the desired sector. sstf algorithm selects the minimum seek time from the current head position.

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  • Quickest way to write to file in java

    - by user1097772
    I'm writing an application which compares directory structure. First I wrote an application which writes gets info about files - one line about each file or directory. My soulution is: calling method toFile Static PrintWriter pw = new PrintWriter(new BufferedWriter( new FileWriter("DirStructure.dlis")), true); String line; // info about file or directory public void toFile(String line) { pw.println(line); } and of course pw.close(), at the end. My question is, can I do it quicker? What is the quickest way? Edit: quickest way = quickest writing in the file

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  • File IO, Handling CRLF

    - by aCuria
    Hi, i am writing a program that takes a file and splits it up into multiple small files of a user specified size, then join the multiple small files back again. 1) the code must work for c, c++ 2) i am compiling with multiple compilers. I am reading and writing to the files by using the stl functions fread() and fwrite() The problem I am having pertains to CRLF. If the file I am reading from contains CRLF, then I want to retain it when i split and join the files back together. If the file contains LF, then i want to retain LF. Unfortunately, fread() seems to store CRLF as \n (I think), and whatever is written by fwrite() is compiler-dependent. How do i approach this problem? Thanks.

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  • Recursive QuickSort suffering a StackOverflowException -- Need fresh eyes

    - by jon
    I am working on a Recursive QuickSort method implementation in a GenericList Class. I will have a second method that accepts a compareDelegate to compare different types, but for development purposes I'm sorting a GenericList<int I am recieving stackoverflow areas in different places depending on the list size. I've been staring at and tracing through this code for hours and probably just need a fresh pair of (more experienced)eyes. Definitely wanting to learn why it is broken, not just how to fix it. public void QuickSort() { int i, j, lowPos, highPos, pivot; GenericList<T> leftList = new GenericList<T>(); GenericList<T> rightList = new GenericList<T>(); GenericList<T> tempList = new GenericList<T>(); lowPos = 1; highPos = this.Count; if (lowPos < highPos) { pivot = (lowPos + highPos) / 2; for (i = 1; i <= highPos; i++) { if (this[i].CompareTo(this[pivot]) <= 0) leftList.Add(this[i]); else rightList.Add(this[i]); } leftList.QuickSort(); rightList.QuickSort(); for(i=1;i<=leftList.Count;i++) tempList.Add(leftList[i]); for(i=1;i<=rightList.Count;i++) tempList.Add(rightList[i]); this.items = tempList.items; this.count = tempList.count; } }

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  • calling a function from another function in python

    - by user1040503
    I have written this function that takes to strings in order to see if they are anagrams: def anagram_check(str_x, str_y): x = string1.replace(" ","") y = string2.replace(" ","") lower1 = x.lower() lower2 = y.lower() sorted1 = sorted(lower1) sorted2 = sorted(lower2) if sorted1 == sorted2: return True else: return False this function works fine, the problem is that now I need to use this function in another function in order to find anagrams in a text file. I want to print a list of tuples with all the anagrams in it. this is what i have done so far def anagrams_finder(words_num): anagrams = [] f = open("words.txt") a = list(f) list1 = ([s.replace('\n', '') for s in a]) list2 = ([i.lower() for i in list1]) list3 = list2[0:words_num] #number of words from text that need to be checked. for i in list3: .... I tried using for loops, while loops, appand.... but nothing seems to work. how can I use the first function in order to help me with the second? Please help...

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  • Still failing a function, not sure why...ideas on test cases to run?

    - by igor
    I've been trying to get this Sudoku game working, and I am still failing some of the individual functions. All together the game works, but when I run it through an "autograder", some test cases fail.. Currently I am stuck on the following function, placeValue, failing. I do have the output that I get vs. what the correct one should be, but am confused..what is something going on? EDIT: I do not know what input/calls they make to the function. What happens is that "invalid row" is outputted after every placeValue call, and I can't trace why.. Here is the output (mine + correct one) if it's at all helpful: http://pastebin.com/Wd3P3nDA Here is placeValue, and following is getCoords that placeValue calls.. void placeValue(Square board[BOARD_SIZE][BOARD_SIZE]) { int x,y,value; if(getCoords(x,y)) { cin>>value; if(board[x][y].permanent) { cout<< endl << "That location cannot be changed"; } else if(!(value>=1 && value<=9)) { cout << "Invalid number"<< endl; clearInput(); } else if(validMove(board, x, y, value)) { board[x][y].number=value; } } } bool getCoords(int & x, int & y) { char row; y=0; cin>>row>>y; x = static_cast<int>(toupper(row)); if (isalpha(row) && (x >= 'A' && x <= 'I') && y >= 1 && y <= 9) { x = x - 'A'; // converts x from a letter to corresponding index in matrix y = y - 1; // converts y to corresponding index in matrix return (true); } else if (!(x >= 'A' && x <= 'I')) { cout<<"Invalid row"<<endl; clearInput(); return false; } else { cout<<"Invalid column"<<endl; clearInput(); return false; } }

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  • Find if there is an element repeating itself n/k times

    - by gleb-pendler
    You have an array size n and a constant k (whatever) You can assume the the array is of int type (although it could be of any type) Describe an algorithm that finds if there is an element(s) that repeats itself at least n/k times... if there is return one. Do so in linear time (O(n)) The catch: do this algorithm (or even pseudo-code) using constant memory and running over the array only twice

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  • Interview question: How do I detect a loop in this linked list?

    - by jjujuma
    Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a constant amount of space and a reasonable amount of time? Here's a picture of what a list with a loop looks like: Node->Node->Node->Node->Node->Node--\ \ | ----------------

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  • File processing-Haskell

    - by Martinas Maria
    How can I implement in haskell the following: I receive an input file from the command line. This input file contains words separated with tabs,new lines and spaces.I have two replace this elements(tabs,new lines and spaces) with comma(,) .Observation:more newlines,tabs,spaces will be replaced with a single comma.The result has to be write in a new file(output.txt). Please help me with this.My haskell skills are very scarse. This is what I have so far: processFile::String->String processFile [] =[] processFile input =input process :: String -> IO String process fileName = do text <- readFile fileName return (processFile text) main :: IO () main = do n <- process "input.txt" print n In processFile function I should process the text from the input file. I'm stuck..Please help.

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  • Finding if a path between 2 sides of a game board exists

    - by Meny
    Hi, i'm currently working on a game as an assignment for school in java. the game cuurently is designed for Console. the game is for 2 players, one attacking from north to south, and the other from west to east. the purpose of the game is to build a "bridge"/"path" between the 2 of your sides before your opponent does. for example: A B C D E F 1 _ _ X _ _ _ 1 2 O X X _ _ _ 2 3 O X O O O O 3 4 O X O _ _ _ 4 5 X X _ _ _ _ 5 6 X O _ _ _ _ 6 A B C D E F player that attacks from north to south won (path/bridge from C to A) my problem is, what algorithm would be good to check if the user have managed to create a path (will be checked at the end of each turn). you're help would be very appreciated.

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  • SQL to display an event on start date, end date and any days in between.

    - by Tim
    Hello, This should be fairly simple, but I can't get my head around it. I have an event in my database with a startDate and an endDate. I need to display this event (based on the current date) on every day the event occurs. So if the event starts on the 3rd of May and finishes on the 7th of May, the SQL query must find it on every single day. How can I achieve this? SELECT * FROM events WHERE startDate ??? Thanks, Tim

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  • Programming help Loop adding

    - by Deonna
    I know this probably really simple but Im not sure what im doing wrong... The assignment states: For the second program for this lab, you are to have the user enter an integer value in the range of 10 to 50. You are to verify that the user enters a value in that range, and continue to prompt him until he does give you a value in that range. After the user has successfully entered a value in that range, you are to display the sum of all the integers from 1 to the value entered. I have this so far: #include <iostream.h> int main () { int num, sum; cout << "do-while Loop Example 2" << endl << endl; do { cout << "Enter a value from 10 to 50: "; cin >> num; if (num < 10 || num > 50) cout << "Out of range; Please try again..." << endl; } while (num < 10 || num > 50); { int i; int sum = 0; for (num = 1; num <= 50; num ++) sum = sum + num; } cout << endl << "The sum is " << sum << endl; return 0; } Im just not sure exactly what i'm doing wrong... I keep getting the wrong sum for the total...

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  • Encapsulating user input of data for a class (C++)

    - by Dr. Monkey
    For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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  • How do I cast a void pointer to a struct in C?

    - by Rowhawn
    In a project I'm writing code for, I have a void pointer, "implementation", which is a member of a "Hash_map" struct, and points to an "Array_hash_map" struct. The concepts behind this project are not very realistic, but bear with me. The specifications of the project ask that I cast the void pointer "implementation" to an "Array_hash_map" before I can use it in any functions. My question, specifically is, what do I do in the functions to cast the void pointers to the desired struct? Is there one statement at the top of each function that casts them or do I make the cast every time I use "implementation"? Here are the typedefs the structs of a Hash_map and Array_hash_map as well as a couple functions making use of them. typedef struct { Key_compare_fn key_compare_fn; Key_delete_fn key_delete_fn; Data_compare_fn data_compare_fn; Data_delete_fn data_delete_fn; void *implementation; } Hash_map; typedef struct Array_hash_map{ struct Unit *array; int size; int capacity; } Array_hash_map; typedef struct Unit{ Key key; Data data; } Unit; functions: /* Sets the value parameter to the value associated with the key parameter in the Hash_map. */ int get(Hash_map *map, Key key, Data *value){ int i; if (map == NULL || value == NULL) return 0; for (i = 0; i < map->implementation->size; i++){ if (map->key_compare_fn(map->implementation->array[i].key, key) == 0){ *value = map->implementation->array[i].data; return 1; } } return 0; } /* Returns the number of values that can be stored in the Hash_map, since it is represented by an array. */ int current_capacity(Hash_map map){ return map.implementation->capacity; }

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  • asking the container to notify your application whenever a session is about to timeout in Java

    - by user136101
    Which method(s) can be used to ask the container to notify your application whenever a session is about to timeout?(choose all that apply) A. HttpSessionListener.sessionDestroyed -- correct B. HttpSessionBindingListener.valueBound C. HttpSessionBindingListener.valueUnbound -- correct this is kind of round-about but if you have an attribute class this is a way to be informed of a timeout D. HttpSessionBindingEvent.sessionDestroyed -- no such method E. HttpSessionAttributeListener.attributeRemoved -- removing an attribute isn’t tightly associated with a session timeout F. HttpSessionActivationListener.sessionWillPassivate -- session passivation is different than timeout I agree with option A. 1) But C is doubtful How can value unbound be tightly coupled with session timeout.It is just the callback method when an attribute gets removed. 2) and if C is correct, E should also be correct. HttpSessionAttributeListener is just a class that wants to know when any type of attribute has been added, removed, or replaced in a session. It is implemented by any class. HttpSessionBindingListener exists so that the attribute itself can find out when it has been added to or removed from a session and the attribute class must implement this interface to achieve it. Any ideas…

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  • Check if there are any repeated elements in an array recursively

    - by devoured elysium
    I have to find recursively if there is any repeated element in an integer array v. The method must have the following signature: boolean hasRepeatedElements(int[] v) I can't see any way of doing that recursively without having to define another method or at least another overload to this method (one that takes for example the element to go after or something). At first I thought about checking for the current v if there is some element equal to the first element, then creating a new array with L-1 elements etc but that seems rather inefficient. Is it the only way? Am I missing here something?

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  • Finding an available network port on the machine

    - by Tomer Vromen
    I'm trying to implement a simple FTP server (a variation of the EFTP protocol) in linux. When a client connects and sends the PASV command, the server should respond with a port number, so the client can connect to that port to transmit the file. How can the server choose a port number? Do I need to iterate through all the ports from 1024 to 65535 until I find a port that the process can bind to? I know that calling bind() with 0 as the port automatically chooses the port to bind to, but then how can I know which port was chosen? Many thanks.

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