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  • c++ polymorphism and other function question

    - by aharont
    i have got this code: class father{ public: virtual void f() { cout<<1;} }; class son:public father{ public: void f() {cout<<2;} }; void test (father x){x.f();} int main(){ son s; test(s); } the question says: the output is '1', what is the rule about polymorphism that the programmer forgot and how can i fix it so the output would be '2'? there is another rule that the programmer forgot when he wrote the father class, and he need to add an empty function to avoid problems from other sons of the father class. what is the rule and what is the missing function? another question write the g function so the next code would run with no crashes int x=11; g(x)=22;

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  • Convert integer to equivalent number of blank spaces.

    - by mike
    I was wondering what the easiest way is to convert an integer to the equivalent number of blank spaces. I need it for the spaces between nodes when printing a binary search tree. I tried this `int position = printNode.getPosition(); String formatter = "%1"+position+"s%2$s\n"; System.out.format(formatter, "", node.element);` But I am getting almost 3 times as many spaces compared to the int value of position. I'm not really sure if I am formatting the string right either. Any suggestions would be great! If it makes it clearer, say position = 6; I want 6 blank spaces printed before my node element.

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  • A hard Question ?

    - by the-ifl
    Hi Guys , I try To find a solution to a question .... we have a number , example : 20 ... and we have 6 number :{ a ,b , c , d , e , f} < 20 , t try to find all values of these numbers , but only if we can combinate (whit + or -) whit 2 of this numbers and getting all the value below to 20 : for example we choose 31 : a = 22 b = 21 c = 14 d = 11 e = 9 f = 5 we have : 22 - 21 = 1 ; 11 - 9 = 2 ; 14 - 11 = 3 ; 9 - 5 = 4 ; f = 5 ; 11 - 5 = 6 ; 21 - 14 = 7 ; .... .... .... .... .... 21 + 9 = 30 ; 9 + 22 = 31 ;

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  • fwrite C programing

    - by Pedro
    HI...i want to write something like this in a file, using fwrite fwrite("name is %s\n",name, 60, fp); but is not working, only write in the file the string. any idea?

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  • My PHP script for sending emails wont send

    - by James
    Well I'm working on a school project, and I uploaded my script to send emails. I'm pretty much using whats defined here: http://www.webcheatsheet.com/PHP/send_email_text_html_attachment.php . Now, all I really changed(other than the contents), is the receiver, to my email address. However, I'm not getting it in my inbox. Is there something else I need? Do I need to do something with the settings on the server(or have my school enable something)?

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  • Java cannot find symbol enum

    - by JDelage
    Hi, I'm modeling a chess game on Java, and I'm having some problem. Here's what the code looks like (the relevant parts): Enum class Couleur.java: public enum Couleur {BLANC, NOIR} Piece.java: public abstract class Piece { (...) public Piece(Couleur couleurParam){ this.couleurPiece = couleurParam; } (...) } And finally Tour.java: public class Tour extends Piece { (...) public Tour(Couleur couleurParam){ super(couleurParam); } (...) } All the .java files are in the same folder. Yet at compile I get a "cannot find symbol symbol : variable NOIR location: class Plateau" (Plateau is the class that instantiates Tour.) Can anyone help me figure out what's wrong here? Many thanks, JDelage

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  • Getter/Setter from separate class file in Java

    - by Crystal
    I'm new to Java and for a HW assignment, we had to create a Person class that has a constructor, getter/setter for the attributes of firstName, lastName, phone. That is in a separate file from an old HW assignment (Person.java). Now we have to use that Person class in our new HW assignment (LoanApplication.java). So if one of the attributes is private Person client do I need to create getter/setters or a constructor again? Otherwise, how does each LoanApplicaiton instance know which Person attribute it is to go with? How does the JVM know that it can use the Person.class even though my LoanApplicaiton.class does not extend Person.class? Thanks.

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  • C Programming - Passing a pointer to array

    - by Pedro
    How do I pass a pointer value to an array of the struct; For example, on a txt I have this: John Doe;[email protected];214425532; My code: typedef struct Person{ char name[100]; char email[100]; int phone; }PERSON; int main(){ PERSON persons[100]; FILE *fp; char *ap_name; char *ap_email; char *ap_phone; char line[100]; fp=("text.txt","r"); if(fp==NULL){ exit(1); } else{ fgets(line,100,fp); ap_name=strtok(line,";"); ap_email=strtok(NULL,";"); ap_phone=strtok(NULL,";"); } return 0; } My question is how can I pass the value of ap_name, ap_email, ap_phone to the struct? And, do I need to use all of these pointers?

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  • C programing some errors :(

    - by Pedro
    Hi...this is a little code that i'm doing, but i have some errors...:S Hi have a txt file and i want to "convert to xml", but the program must know what is comments, and must organize... txt file: /* Licenciaturas na ESTG-IPVC 2009 – v1.1*/ - Info, <N Alunos> <hr>--------------------------------------------------- 3 <hr>--------------------------------------------------- - data, <course><Number>;<name>;<email> - disciplinas, <n disciplines>;<note>;[<note>;] </hr>--------------------------------------------------- LEI;7671;Name name name;[email protected]; 9;8;12;9;12;11;6;15;7;11; LTCGM;6567;nam1 nam2 nam3;[email protected]; 6;13;14;12;11;16;14; LEI;7701;xxxxx xxxx xxxx;[email protected]; 8;13;11;7;14;12;11;16;14; My code: int main(int argc, char *argv[]) { char first[60];//array char comment[60];//array char nome_int[60];//array char total[60];//array char course[60];//array int i; char notas[60]; char *number, *name, *mail, *total_disci; int total_cad; char disciplines[60]; printf("Int. the name of the file to convert\n"); scanf("%s",&nome_int); FILE *fp = fopen(nome_int, "r"); //open file FILE *conver = fopen("conver.xml","w");// opne output FILE *coment = fopen("coment.txt","w"); if (fp == NULL) { printf("File not found\n"); exit(1); } else { fgets(first, 60,fp); fputs(first,coment); while (!(feof(fp))){ fgets(first, 60, fp); if (first[0] == '-'){ fputs(first,coment); } for(i=1;fscanf(fp,"%s",total)!=-5;i++){ if(i==2){ printf("Total %s",total);//here the program stops } } fgets(course,60,fp); if(course[0]=='L'){ number = strchr(course, ';');//here course is an array but must be an appointer, what can i do? *number = '\0'; number++; name = strchr(number, ';'); *name = '\0'; name++; mail= strchr(name, ';'); *mail = '\0'; mail++; char *curso1; total_cad=atoi(total_disci); printf("Course: %s\n",course); printf("Number: %s\n",number); printf("Name: %s\n",name); printf("e-mail: %s\n",mail); } fgets(disciplines,60,fp);//here crash total_disci= strchr(mail, ';'); *total_disci = '\n'; total_disci++; printf("Total disciplines: %d\n",total_cad); } } fclose(fp); fclose(coment); fclose(conver); system("PAUSE"); return 0; } the convert file must be like this: <xml> <list_courses> <course> <sigla>LEI</sigla> <NAlunos>2</NAlunos> <list_students> <students> <number>7671</number> <name>name name name</name> <email>[email protected]</email> <stat>disaproved</stat> <media_notes>10</media_notes> <biggest_note>15</biggest_note> <small_nota>6</small_nota> </students> </list_students> </course> </list_courses> </xml> _______________________________________- now separated by only comment on what is what and converted to xml. also had to do was impressed that the program could name, email address, number, etc. .. here the main errors do not want to do for me, just want to see the errors, I spent the whole day right back from them and nothing ... someone who can help, please do it :)

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  • complex arguments for function

    - by myPost1
    My task is to create function funCall taking four arguments : pointer for 2d array of ints that stores pairs of numbers variable int maintaining number of numbers in 2d array pointer for table of pointers to functions int variable storing info about number of pointers to functions I was thinking about something like this : typedef int(*funPtr)(int, int); funPtr arrayOfFuncPtrs[]; void funCall( *int[][]k, int a, *funPtr z, int b); { }

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  • sloving Algorithm notation

    - by neednewname
    Use big-O notation to classify the traditional grade school algorithms for addition and multiplication. That is, if asked to add two numbers each having N digits, how many individual additions must be performed? If asked to multiply two N-digit numbers, how many individual multiplications are required Suppose f is a function that returns the result of reversing the string of symbols given as its input, and g is a function that returns the concatenation of the two strings given as its input. If x is the string hrwa, what is returned by g(f(x),x)? Explain your answer - don't just provide the result!

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  • output all data from db to a php page

    - by Sarit
    Hi, I'm a real beginner with PHP & mysql. Just for studying and for a simple example at school I would like to work this simple query and possibly output all the rows (or maybe even one) to a very basic output on a php page: <?php $user= "root"; $host="localhost"; $password=""; $database = "PetCatalog"; $cxn = mysqli_connect($host,$user,$password,$database) or die ("couldn’t connect to server"); $query = "SELECT * FROM Pet"; $result = mysql_query($cxn,$query) or die ("Couldn’t execute query."); $row = mysqli_fetch_assoc($result); echo "$result"; ?> this is the error message i've been getting: Warning: mysql_query() expects parameter 1 to be string, object given in C:\xampplite\htdocs\myblog\query.php on line 18 Couldn’t execute query. What should I do? Thanks!

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  • How can I implement a splay tree that performs the zig operation last, not first?

    - by Jakob
    For my Algorithms & Data Structures class, I've been tasked with implementing a splay tree in Haskell. My algorithm for the splay operation is as follows: If the node to be splayed is the root, the unaltered tree is returned. If the node to be splayed is one level from the root, a zig operation is performed and the resulting tree is returned. If the node to be splayed is two or more levels from the root, a zig-zig or zig-zag operation is performed on the result of splaying the subtree starting at that node, and the resulting tree is returned. This is valid according to my teacher. However, the Wikipedia description of a splay tree says the zig step "will be done only as the last step in a splay operation" whereas in my algorithm it is the first step in a splay operation. I want to implement a splay tree that performs the zig operation last instead of first, but I'm not sure how it would best be done. It seems to me that such an algorithm would become more complex, seeing as how one needs to find the node to be splayed before it can be determined whether a zig operation should be performed or not. How can I implement this in Haskell (or some other functional language)?

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  • Recursion problem in algorithm

    - by Marthin
    I'm not sure if this is the right place to post this, but the problem actually belongs to a programming assignment. Solve the recursion: T(0) = 2; T(n) = T(n-1) + 2; Solution: T(n) = 2(n+1) Could someone please show me how they got to that solution?

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  • Efficient Multiplication of Varying-Length #s [Conceptual]

    - by Milan Patel
    Write the pseudocode of an algorithm that takes in two arbitrary length numbers (provided as strings), and computes the product of these numbers. Use an efficient procedure for multiplication of large numbers of arbitrary length. Analyze the efficiency of your algorithm. I decided to take the (semi) easy way out and use the Russian Peasant Algorithm. It works like this: a * b = a/2 * 2b if a is even a * b = (a-1)/2 * 2b + a if a is odd My pseudocode is: rpa(x, y){ if x is 1 return y if x is even return rpa(x/2, 2y) if x is odd return rpa((x-1)/2, 2y) + y } I have 3 questions: Is this efficient for arbitrary length numbers? I implemented it in C and tried varying length numbers. The run-time in was near-instant in all cases so it's hard to tell empirically... Can I apply the Master's Theorem to understand the complexity...? a = # subproblems in recursion = 1 (max 1 recursive call across all states) n / b = size of each subproblem = n / 1 - b = 1 (problem doesn't change size...?) f(n^d) = work done outside recursive calls = 1 - d = 0 (the addition when a is odd) a = 1, b^d = 1, a = b^d - complexity is in n^d*log(n) = log(n) this makes sense logically since we are halving the problem at each step, right? What might my professor mean by providing arbitrary length numbers "as strings". Why do that? Many thanks in advance

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  • Linked lists in Java - Help with writing methods

    - by user368241
    Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. 1) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Here is my try : public int indexOf (int ch) { int count = 0; charNode pos = _head; if (pos == null ) { return -1; } for (pos = _head; pos!=null && pos.getData()!=ch; pos = pos.getNext()) { count = count + pos.getValue(); } if (pos==null) return -1; return count; } Time complexity = O(N) Space complexity = O(1) EDIT : I have a problem. I tested it in BlueJ and if the char ch doesn't appear it returns -1 but if it does, it always returns 0 and I don't understand why... I am confused. How can the compiler know that the value is the number of times the letter appears consecutively? Can I assume this because its given on the question or what? If it's true and I can assume this, then my code should be correct right? Ok I just spoke with my instructor and she said it isn't required to write it in the exercise but in order for me to test that it indeed works, I need to open a new class and write a code for making a list so that the the value of every node is the number of times the letter appears consecutively. Can someone please assist me? So I will copy+paste to BlueJ and this way I will be able to test all the methods. Meanwhile I am moving on to the next methods. 2) public int indexOf (int ch, int fromIndex) - returns the index in the string it is operated on of the first appeareance of the char "ch", as the search begins in the index "fromIndex". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex doesn't appear in the range, returns -1. Here is my try: public int indexOf (int ch, int fromIndex) { int count = 0, len=0, i; charNode pos = _head; CharNode cur = _head; for (pos = _head; pos!=null; pos = pos.getNext()) { len = len+1; } if (fromIndex<0 || fromIndex>=len) return -1; for (i=0; i<fromIndex; i++) { cur = cur.getNext(); } if (cur == null ) { return -1; } for (cur = _head; cur!=null && cur.getData()!=ch; cur = cur.getNext()) { count = count + cur.getValue(); } if (cur==null) return -1; return count; } Time complexity = O(N) ? Space complexity = O(1) 3) public StringList concat (String str) - returns a string that consists of the string that it is operated on and in its end the string "str" is concatenated. Here is my try : public StringList concat (String str) { String str = ""; charNode pos = _head; if (str == null) return -1; for (pos = _head; pos!=null; pos = pos.getNext()) { str = str + pos.getData(); } str = str + "str"; return str; } Time complexity = O(N) Space complexity = O(1)

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  • question about missing element in array

    - by davit-datuashvili
    i have following problem from book introduction algorithm second edition by MIT university problem is following An array A[1 . . n] contains all the integers from 0 to n except one. It would be easy to determine the missing integer in O(n) time by using an auxiliary array B[0 . . n] to record which numbers appear in A. In this problem, however, we cannot access an entire integer in A with a single operation. The elements of A are represented in binary, and the only operation we can use to access them is “fetch the j th bit of A[i],” which takes constant time. Show that if we use only this operation, we can still determine the missing inte- ger in O(n) time please help

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  • Very difficult SQL query

    - by db666
    For the following table definitions: Name Null? Type Comments ------------------------------- -------- ---- ------------------------------------ ENUM NOT NULL NUMBER(4) ENUM should not exceed a length of 4. ENAME CHAR(15) ADDRESS CHAR(25) ADDRESS should not exceed 25 characters. SALARY NUMBER(5) OFFICE CHAR(4) DNUM NOT NULL NUMBER(4) Department which this employee belongs to department Name Null? Type Comments ------------------------------- -------- ---- ------------------------------------- DNUM NOT NULL NUMBER(4) DMGR NOT NULL NUMBER(4) Department manager DNAME NOT NULL CHAR(15) project Name Null? Type Comments ------------------------------- -------- ---- ------------------------------------- PNUM NOT NULL NUMBER(4) PMGR NOT NULL NUMBER(4) Project manager PTITLE NOT NULL CHAR(15) emp_proj Name Null? Type ------------------------------- -------- ---- PNUM NOT NULL NUMBER(4) ENUM NOT NULL NUMBER(4) I have to write SQL query which will find the names of employees who do not share an office but work on the same project, and have different salaries... I've spent last three days trying to figure out something, but no idea as far. I will appreciate any advice.

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  • Catching the return of main function before it deallocates resources

    - by EpsilonVector
    I'm trying to implement user threads in Linux kernel 2.4, and I ran into something problematic and unexpected. Background: a thread basically executes a single function and dies, except that when I call thread_create for the first time it must turn main() into a thread as well (by default it is not a thread until the first call, which is also when all the related data structures are allocated). Since a thread executes a function and dies, we don't need to "return" anywhere with it, but we do need to save the return value to be reclaimed later with thread_join, so the hack I came up with was: when I allocate the thread stack I place a return address that points to a thread_return_handler function, which deallocates the thread, makes it a zombie, and saves its return value for later. This works for "just run a function and die" threads, but is very problematic with the main thread. Since it actually is the main function, if it returns before the other threads finish the normal return mechanism kicks in, and deallocates all the shared resources, thus screwing up all the running threads. I need to keep it from doing that. Any ideas on how it can be done?

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  • Returnimng collection of interfaces

    - by apoorv020
    I have created the following interface public interface ISolutionSpace { public boolean isFeasible(); public boolean isSolution(); public Set<ISolutionSpace> generateChildren(); } However, in the implementation of ISolutionSpace in a class called EightQueenSolutionSpace, I am going to return a set of EightQueenSolutionSpace instances, like the following stub: @Override public Set<ISolutionSpace> generateChildren() { return new HashSet<EightQueenSolutionSpace>(); } However this stub wont compile. What changes do I need to make? EDIT: I tried 'HashSet' as well and had tried using the extends keyword. However since 'ISolutionSpace' is an interface and EightQueenSolutionSpace is an implementation(and not a subclass) of 'ISolutionSpace', it is still not working.

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  • GoTo statements and alternatives in VB.NET

    - by qais
    I've posted a code snippet on another forum asking for help and people pointed out to me that using GoTo statements is very bad programming practice. I'm wondering: why is it bad? What alternatives to GoTo are there to use in VB.NET that would be considered generally more of a better practice? Consider this snippet below where the user has to input their date of birth. If the month/date/year are invalid or unrealistic(using if statements checking the integer inputs size, if there's a better way to do this, I'd appreciate if you could tell me that also :D) How would I be able to loop back to ask the user again? retryday: Console.WriteLine("Please enter the day you were born : ") day = Console.ReadLine If day > 31 Or day < 1 Then Console.WriteLine("Please enter a valid day") GoTo retryday End If

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