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  • What does [a|b|c] evaluate to in Prolog?

    - by Ambrose
    The pipe operator in prolog returns one or more atomic Heads and a Tail list. ?- [a,b,c] = [a,b|[c]]. true. Nesting multiple pipes in a single match can be done similar to this: ?- [a,b,c] = [a|[b|[c]]]. true. What does the statement [a|b|c] infer about a, b and c?

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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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  • 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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  • 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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  • MPI Odd/Even Compare-Split Deadlock

    - by erebel55
    I'm trying to write an MPI version of a program that runs an odd/even compare-split operation on n randomly generated elements. Process 0 should generated the elements and send nlocal of them to the other processes, (keeping the first nlocal for itself). From here, process 0 should print out it's results after running the CompareSplit algorithm. Then, receive the results from the other processes run of the algorithm. Finally, print out the results that it has just received. I have a large chunk of this already done, but I'm getting a deadlock that I can't seem to fix. I would greatly appreciate any hints that people could give me. Here is my code http://pastie.org/3742474 Right now I'm pretty sure that the deadlock is coming from the Send/Recv at lines 134 and 151. I've tried changing the Send to use "tag" instead of myrank for the tag parameter..but when I did that I just keep getting a "MPI_ERR_TAG: invalid tag" for some reason. Obviously I would also run the algorithm within the processors 0 but I took that part out for now, until I figure out what is going wrong. Any help is appreciated.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • staying within boundaries of image?

    - by codefail
    So I am to loop through copyFrom.pixelData and copy it into pixelData. I realize that I need to check the conditions of i and j, and have them not copy past the boundaries of pixelData[x][y], I need another 2 loops for that? I tried this, but was getting segmentation fault.. Is this the right approach? void Image::insert(int xoff, int yoff, const Image& copyFrom, Color notCopy) { for (int x = xoff; x < xoff+copyFrom.width; x++) { for (int y = yoff; y < yoff+copyFrom.height; y++) { for (int i = 0; i<width; i++){ for (int j = 0; j<height; j++){ if (copyFrom.pixelData[i][j].colorDistance(notCopy)>20 ) pixelData[x][y]=copyFrom.pixelData[i][j]; } } } } }

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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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  • m:n relationship must have properties?

    - by nax
    I'm doing a E/R model for a project. I finished the ER model and, for me, all is okay. Maybe not perfect, but it's okay. When I gave the ER model to my teacher, he told me this: "the m:n relations MUST HAVE some properties" He said if the m:n relationship doesn't have the properties it will be wrong. In my opinion m:n doesn't need forcer attributes to the relationship, but if you have someone that can fit in it, just put there. What do you think? Who is wrong in this, me, or my teacher? NOTE: Reading again, it seems what he said was not due to my ER diagram, but was a general statement. The diagram I gave him doesn't have relations yet, so there where just entities and atributes.

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  • C programming - How to print numbers with a decimal component using only loops?

    - by californiagrown
    I'm currently taking a basic intro to C programming class, and for our current assignment I am to write a program to convert the number of kilometers to miles using loops--no if-else, switch statements, or any other construct we haven't learned yet are allowed. So basically we can only use loops and some operators. The program will generate three identical tables (starting from 1 kilometer through the input value) for one number input using the while loop for the first set of calculations, the for loop for the second, and the do loop for the third. I've written the entire program, however I'm having a bit of a problem with getting it to recognize an input with a decimal component. Here is what I have for the while loop conversions: #include <stdio.h> #define KM_TO_MILE .62 main (void) { double km, mi, count; printf ("This program converts kilometers to miles.\n"); do { printf ("\nEnter a positive non-zero number"); printf (" of kilometers of the race: "); scanf ("%lf", &km); getchar(); }while (km <= 1); printf ("\n KILOMETERS MILES (while loop)\n"); printf (" ========== =====\n"); count = 1; while (count <= km) { mi = KM_TO_MILE * count; printf ("%8.3lf %14.3lf\n", count, mi); ++count; } getchar(); } The code reads in and converts integers fine, but because the increment only increases by 1 it won't print a number with a decimal component (e.g. 3.2, 22.6, etc.). Can someone point me in the right direction on this? I'd really appreciate any help! :)

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  • Trouble with arraylist and stack

    - by helloman
    I am having trouble starting out this program, I am suppose to write a program that will create an ArrayList, asking the user for 10 numbers. Then this will be put into the Array. Then after the list is made navigate it and if a number is even remove it from the ArrayList and copy it to a stack of integers. import java.io.* ; import java.util.*; public class Test { public static void main(String[] args){ Scanner input = new Scanner (System.in); ArrayList<Integer> integers = new ArrayList<Integer>(); System.out.print ("Enter Number: \n"); for (int i = 0; i < 10; i++){ integers.add(input.nextInt()); } for (int i = 0; i < 10 ; i++){ if (i %2==0) } } }

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  • C++. What is a subprogram and method?

    - by xbonez
    I have a CPP HW to be done. One question is: 1) Write a subprogram (not a method) void promptForMovie(Movie & myMovie) that ..... 2) Write a method void output(ostream & out); that .... My question is what exactly is a subprogram and a method? Which one of them means a function, and what does the other mean? Thank you

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  • two classes contain objects of each other

    - by Julz
    hi, i hope there's a simple answer to this. without getting too complicated i have two classes. an "Animal" and a "Cell" Cell contains an Animal as a member. Animal has methods that accept Cells in their parameters. i'm just confused as to how i #include each class the others header? i've only ever had to go up a chain of classes and just included the last class header in the next and so on, but this circular situation has me a bit lost. i hope that makes sense, any help greatly appreciated.

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  • Simple 'database' in c++

    - by DevAno1
    Hello. My task was to create pseudodatabase in c++. There are 3 tables given, that store name(char*), age(int), and sex (bool). Write a program allowing to : - add new data to the tables - show all records - sort tables with criteria : - name increasing/decreasing - age increasing/decreasing - sex Using function templates is a must. Also size of arrays must be variable, depending on the amount of records. I have some code but there are still problems there. Here's what I have: Function tabSize() for returning size of array. But currently it returns size of pointer I guess : #include <iostream> using namespace std; template<typename TYPE> int tabSize(TYPE *T) { int size = 0; size = sizeof(T) / sizeof(T[0]); return size; } How to make it return size of array, not its pointer ? Next the most important : add() for adding new elements. Inside first I get the size of array (but hence it returns value of pointer, and not size it's of no use now :/). Then I think I must check if TYPE of data is char. Or am I wrong ? // add(newElement, table) template<typename TYPE> TYPE add(TYPE L, TYPE *T) { int s = tabSize(T); //here check if TYPE = char. If yes, get the length of the new name int len = 0; while (L[len] != '\0') { len++; } //current length of table int tabLen = 0; while (T[tabLen] != '\0') { tabLen++; } //if TYPE is char //if current length of table + length of new element exceeds table size create new table if(len + tabLen > s) { int newLen = len + tabLen; TYPE newTab = new [newLen]; for(int j=0; j < newLen; j++ ){ if(j == tabLen -1){ for(int k = 0; k < len; k++){ newTab[k] = } } else { newTab[j] = T[j]; } } } //else check if tabLen + 1 is greater than s. If yes enlarge table by 1. } Am I thinking correct here ? Last functions show() is correct I guess : template<typename TYPE> TYPE show(TYPE *L) { int len = 0; while (L[len] == '\0') { len++; } for(int i=0; i<len; i++) { cout << L[i] << endl; } } and problem with sort() is as follows : Ho can I influence if sorting is decreasing or increasing ? I'm using bubble sort here. template<typename TYPE> TYPE sort(TYPE *L, int sort) { int s = tabSize(L); int len = 0; while (L[len] == '\0') { len++; } //add control increasing/decreasing sort int i,j; for(i=0;i<len;i++) { for(j=0;j<i;j++) { if(L[i]>L[j]) { int temp=L[i]; L[i]=L[j]; L[j]=temp; } } } } And main function to run it : int main() { int sort=0; //0 increasing, 1 decreasing char * name[100]; int age[10]; bool sex[10]; char c[] = "Tom"; name[0] = "John"; name[1] = "Mike"; cout << add(c, name) << endl; system("pause"); return 0; }

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  • im writing this code so the user would enter his/her name and followed by his/her marks to get the a

    - by WM
    What if the user wanted to enter his/her grades in the following way: Will 23, 34, 45, 45 how would i get rid of the commas public class StudentAverage { public static void main(String[] args) { int markSum = 0; double average = 0; Scanner input1 = new Scanner(System.in); System.out.print("Enter student record : "); String name = input1.next(); Scanner input2 = new Scanner(input1.nextLine()); int countTotal = 0; while (input2.hasNextInt()) { countTotal++; markSum += input2.nextInt(); } average = markSum / countTotal; // to calculate the total average System.out.print( name + " " + average ); } }

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