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  • Linked List exercise, what am I doing wrong?

    - by Sean Ochoa
    Hey all. I'm doing a linked list exercise that involves dynamic memory allocation, pointers, classes, and exceptions. Would someone be willing to critique it and tell me what I did wrong and what I should have done better both with regards to style and to those subjects I listed above? /* Linked List exercise */ #include <iostream> #include <exception> #include <string> using namespace std; class node{ public: node * next; int * data; node(const int i){ data = new int; *data = i; } node& operator=(node n){ *data = *(n.data); } ~node(){ delete data; } }; class linkedList{ public: node * head; node * tail; int nodeCount; linkedList(){ head = NULL; tail = NULL; } ~linkedList(){ while (head){ node* t = head->next; delete head; if (t) head = t; } } void add(node * n){ if (!head) { head = n; head->next = NULL; tail = head; nodeCount = 0; }else { node * t = head; while (t->next) t = t->next; t->next = n; n->next = NULL; nodeCount++; } } node * operator[](const int &i){ if ((i >= 0) && (i < nodeCount)) throw new exception("ERROR: Invalid index on linked list.", -1); node *t = head; for (int x = i; x < nodeCount; x++) t = t->next; return t; } void print(){ if (!head) return; node * t = head; string collection; cout << "["; int c = 0; if (!t->next) cout << *(t->data); else while (t->next){ cout << *(t->data); c++; if (t->next) t = t->next; if (c < nodeCount) cout << ", "; } cout << "]" << endl; } }; int main (const int & argc, const char * argv[]){ try{ linkedList * myList = new linkedList; for (int x = 0; x < 10; x++) myList->add(new node(x)); myList->print(); }catch(exception &ex){ cout << ex.what() << endl; return -1; } return 0; }

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  • Database warehouse design: fact tables and dimension tables

    - by morpheous
    I am building a poor man's data warehouse using a RDBMS. I have identified the key 'attributes' to be recorded as: sex (true/false) demographic classification (A, B, C etc) place of birth date of birth weight (recorded daily): The fact that is being recorded My requirements are to be able to run 'OLAP' queries that allow me to: 'slice and dice' 'drill up/down' the data and generally, be able to view the data from different perspectives After reading up on this topic area, the general consensus seems to be that this is best implemented using dimension tables rather than normalized tables. Assuming that this assertion is true (i.e. the solution is best implemented using fact and dimension tables), I would like to seek some help in the design of these tables. 'Natural' (or obvious) dimensions are: Date dimension Geographical location Which have hierarchical attributes. However, I am struggling with how to model the following fields: sex (true/false) demographic classification (A, B, C etc) The reason I am struggling with these fields is that: They have no obvious hierarchical attributes which will aid aggregation (AFAIA) - which suggest they should be in a fact table They are mostly static or very rarely change - which suggests they should be in a dimension table. Maybe the heuristic I am using above is too crude? I will give some examples on the type of analysis I would like to carryout on the data warehouse - hopefully that will clarify things further. I would like to aggregate and analyze the data by sex and demographic classification - e.g. answer questions like: How does male and female weights compare across different demographic classifications? Which demographic classification (male AND female), show the most increase in weight this quarter. etc. Can anyone clarify whether sex and demographic classification are part of the fact table, or whether they are (as I suspect) dimension tables.? Also assuming they are dimension tables, could someone elaborate on the table structures (i.e. the fields)? The 'obvious' schema: CREATE TABLE sex_type (is_male int); CREATE TABLE demographic_category (id int, name varchar(4)); may not be the correct one.

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  • Database warehoue design: fact tables and dimension tables

    - by morpheous
    I am building a poor man's data warehouse using a RDBMS. I have identified the key 'attributes' to be recorded as: sex (true/false) demographic classification (A, B, C etc) place of birth date of birth weight (recorded daily): The fact that is being recorded My requirements are to be able to run 'OLAP' queries that allow me to: 'slice and dice' 'drill up/down' the data and generally, be able to view the data from different perspectives After reading up on this topic area, the general consensus seems to be that this is best implemented using dimension tables rather than normalized tables. Assuming that this assertion is true (i.e. the solution is best implemented using fact and dimension tables), I would like to see some help in the design of these tables. 'Natural' (or obvious) dimensions are: Date dimension Geographical location Which have hierarchical attributes. However, I am struggling with how to model the following fields: sex (true/false) demographic classification (A, B, C etc) The reason I am struggling with these fields is that: They have no obvious hierarchical attributes which will aid aggregation (AFAIA) - which suggest they should be in a fact table They are mostly static or very rarely change - which suggests they should be in a dimension table. Maybe the heuristic I am using above is too crude? I will give some examples on the type of analysis I would like to carryout on the data warehouse - hopefully that will clarify things further. I would like to aggregate and analyze the data by sex and demographic classification - e.g. answer questions like: How does male and female weights compare across different demographic classifications? Which demographic classification (male AND female), show the most increase in weight this quarter. etc. Can anyone clarify whether sex and demographic classification are part of the fact table, or whether they are (as I suspect) dimension tables.? Also assuming they are dimension tables, could someone elaborate on the table structures (i.e. the fields)? The 'obvious' schema: CREATE TABLE sex_type (is_male int); CREATE TABLE demographic_category (id int, name varchar(4)); may not be the correct one.

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  • Linked list example using threads

    - by Carl_1789
    I have read the following code of using CRITICAL_SECTION when working with multiple threads to grow a linked list. what would be the main() part which uses two threads to add to linked list? #include <windows.h> typedef struct _Node { struct _Node *next; int data; } Node; typedef struct _List { Node *head; CRITICAL_SECTION critical_sec; } List; List *CreateList() { List *pList = (List*)malloc(sizeof(pList)); pList->head = NULL; InitializeCriticalSection(&pList->critical_sec); return pList; } void AddHead(List *pList, Node *node) { EnterCriticalSection(&pList->critical_sec); node->next = pList->head; pList->head = node; LeaveCriticalSection(&pList->critical_sec); } void Insert(List *pList, Node *afterNode, Node *newNode) { EnterCriticalSection(&pList->critical_sec); if (afterNode == NULL) { AddHead(pList, newNode); } else { newNode->next = afterNode->next; afterNode->next = newNode; } LeaveCriticalSection(&pList->critical_sec); } Node *Next(List *pList, Node *node) { Node* next; EnterCriticalSection(&pList->critical_sec); next = node->next; LeaveCriticalSection(&pList->critical_sec); return next; }

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  • adding elements in to the doubly linked list

    - by user329820
    Hi this is my code for main class and doubly linked class and node class but when I run the program ,in the concole will show this"datastructureproject.DoublyLinkedList@19ee1ac" instead of the random numbers .please help me thanks! main class: public class Main { public static int getRandomNumber(double min, double max) { Random random = new Random(); return (int) (random.nextDouble() * (max - min) + min); } public static void main(String[] args) { int j; int i = 0; i = getRandomNumber(10, 10000); DoublyLinkedList listOne = new DoublyLinkedList(); for (j = 0; j <= i / 2; j++) { listOne.add(getRandomNumber(10, 10000)); } System.out.println(listOne); } } doubly linked list class: public class DoublyLinkedList { private Node head ; private Node tail; private long size = 0; public DoublyLinkedList() { head= new Node(0, null, null); tail = new Node(0, head, null); } public void add(int i){ head.setValue(i); Node newNode = new Node(); head.setNext(newNode); newNode.setPrev(head); newNode = head; } } and the node class is like the class that you have seen before (Node prev,Node next,int value)

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  • Meaning of NEXT in Linked List creation in perl

    - by seleniumnewbie
    So I am trying to learn Linked Lists using Perl. I am reading "Mastering Algorithms with Perl" by Job Orwant. In the book he explains how to create a linked list I understand most of it, but I just simply fail to understand the command/index/key NEXT in the second last line of the code snippet. $list=undef; $tail=\$list; foreach (1..5){ my $node = [undef, $_ * $_]; $$tail = $node; $tail = \${$node->[NEXT]}; # The NEXT on this line? } What is he trying to do there? Isn $node a scalar, which stores the address of the unnamed array. Also even if we are de-referencing $node, should we not refer to the individual elements by an index number example (0,1). If we do use "NEXT" as a key, is $node a reference to a hash? I am very confused. Something in plain English will be highly appreciated.

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  • Java How to find a value in a linked list iteratively and recursively

    - by Roxy
    Hi I have a method that has a reference to a linked list and a int value. So, this method would count and return how often the value happens in the linked list. So, I decided to make a class, public class ListNode{ public ListNode (int v, ListNode n) {value = v; next = n;) public int value; public ListNode next; } Then, the method would start with a public static int findValue(ListNode x, int valueToCount){ // so would I do it like this?? I don't know how to find the value, // like do I check it? for (int i =0; i< x.length ;i++){ valueToCount += valueToCount; } So, I CHANGED this part, If I did this recursively, then I would have public static int findValue(ListNode x, int valueToCount) { if (x.next != null && x.value == valueToCount { return 1 + findValue(x, valueToCount);} else return new findvalue(x, valueToCount); SO, is the recursive part correct now?

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  • How to implement a Linked List in Java?

    - by nbarraille
    Hello! I am trying to implement a simple HashTable in Java that uses a Linked List for collision resolution, which is pretty easy to do in C, but I don't know how to do it in Java, as you can't use pointers... First, I know that those structures are already implemented in Java, I'm not planning on using it, just training here... So I created an element, which is a string and a pointer to the next Element: public class Element{ private String s; private Element next; public Element(String s){ this.s = s; this.next = null; } public void setNext(Element e){ this.next = e; } public String getString(){ return this.s; } public Element getNext(){ return this.next; } @Override public String toString() { return "[" + s + "] => "; } } Of course, my HashTable has an array of Element to stock the data: public class CustomHashTable { private Element[] data; Here is my problem: For example I want to implement a method that adds an element AT THE END of the linked List (I know it would have been simpler and more efficient to insert the element at the beginning of the list, but again, this is only for training purposes). How do I do that without pointer? Here is my code (which could work if e was a pointer...): public void add(String s){ int index = hash(s) % data.length; System.out.println("Adding at index: " + index); Element e = this.data[index]; while(e != null){ e = e.getNext(); } e = new Element(s); } Thanks!

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  • Having trouble deleting a node from a linked list

    - by Requiem
    I've been working on this code for my shell that I'm creating and for some reason it isn't working. I'm implementing a watchuser function that watch's a user when an argument is given (args[1]). However, when a second argument (args[2]) of "off" is given, the user should be deleted from the linked list and should no longer be watched. struct userList * goList; goList = userInventory; do{ if (strcmp(userInventory->username, args[1]) == 0){ printf("%s\n", args[1]); printf("%s\n",userInventory->username); struct userList * temp2; temp2 = userInventory->next; if (userInventory->next != NULL){ userInventory->next = temp2->next; userInventory->next->prev = userInventory; } free(temp2); } goList = goList->next; }while (goList != userInventory); My global struct is also as follows: struct userList{ char * username; struct userList * prev; struct userList * next; } For reason, this code won't delete the user node from my linked list. The adding works, but this remove function won't and I'm not sure why. The print statements are there just to make sure it's executing the condition, which it is. If anyone could help me find the reasoning behind my error, I'd greatly appreciate it. Till then, I'll be trying to debug this. Thanks.

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  • SQL Server 2000 tables

    - by user40766
    We currently have an SQL Server 2000 database with one table containing data for multiple users. The data is keyed by memberid which is an integer field. The table has a clustered index on memberid. The table is now about 200 million rows. Indexing and maintenance are becoming issues. We are debating splitting the table into one table per user model. This would imply that we would end up with a very large number of tables potentially upto the 2,147,483,647, considering just positive values. My questions: Does anyone have any experience with a SQL Server (2000/2005) installation with millions of tables? What are the implications of this architecture with regards to maintenance and access using Query Analyzer, Enterprise Manager etc. What are the implications to having such a large number of indexes in a database instance. All comments are appreciated. Thanks

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  • Handwritten linked list is segfaulting and I don't understand why

    - by Born2Smile
    Hi I was working on a bit of fun, making an interface to run gnuplot from within c++, and for some reason the my linked list implementation fails. The code below fails on the line plots-append(&plot). Stepping through the code I discovered that for some reason the destructor ~John() is called immediately after the constructor John(), and I cannot seem to figure out why. The code included below is a stripped down version operating only on Plot*. Originally I made the linked list as a template class. And it worked fine as ll<int and ll<char* but for some reason it fails as ll<Plot*. Could youp please help me figure out why it fails? and perhaps help me understand how to make it work? In advance: Thanks a heap! //B2S #include <string.h class Plot{ char title[80]; public: Plot(){ } }; class Link{ Plot* element; Link* next; Link* prev; friend class ll; }; class ll{ Link* head; Link* tail; public: ll(){ head = tail = new Link(); head-prev = tail-prev = head-next = tail-next = head; } ~ll(){ while (head!=tail){ tail = tail-prev; delete tail-next; } delete head; } void append(Plot* element){ tail-element = element; tail-next = new Link(); tail-next-prev = tail; tail-next = tail; } }; class John{ ll* plots; public: John(){ plots= new ll(); } ~John(){ delete plots; } John(Plot* plot){ John(); plots-append(plot); } }; int main(){ Plot p; John k(&p); }

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  • Using triggers to update linked server table

    - by tabouakl
    Can I use triggers to insert or update tables in a linked server? I tried it and got the following error: Unable to start a nested transaction for OLE DB provider 'SQLOLEDB'. A nested transaction was required because the XACT_ABORT option was set to OFF. [OLE/DB provider returned message: Cannot start more transactions on this session.] OLE DB error trace [OLE/DB Provider 'SQLOLEDB' ITransactionLocal::StartTransaction returned 0x8004d013: ISOLEVEL=4096].

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  • C++ classes & linked list: adding & counting items

    - by user342289
    I need to make a linked list with classes. Each list will store two values: a URI and IP. After doing all the adding, I need to be able count the total number of items in the linked list. I have tried the following code but it doesn't compile. Any suggestions please? #include <iostream> #include <cstdlib> #include <string> using namespace std; class ip_uri_store { protected: string ip; string uri; ip_uri_store *next; public: ip_uri_store(string huri, string hip); void additem(string auri, string aip); void deleteitem(string duri); void findbyuri(string furi); void findbyip(string fip); int totalitems(); }; ip_uri_store *head = NULL; ip_uri_store *curr = NULL; void ip_uri_store::additem(string auri, string aip) { curr = head; while (curr->next != NULL) { curr = curr->next; } curr->uri = auri; curr->next = new ip_uri_store; curr->ip = aip; curr->next = new ip_uri_store; curr = curr->next; curr = head; } int ip_uri_store::totalitems() { int i = 0; curr = head; while (curr->next != NULL) { i += 1; curr = curr->next; } return i; } int main(int argc, char *argv[]) { if (argc == 1) { cout << "123456, [email protected], Gordon Brown" << endl; return (0); } head = new ip_uri_store; curr = head; int i; for (i = 1; i < argc; i++) { if (argv[i][0] == 'A') //add item { ip_uri_store.additem(argv[i + 1], argv[i + 2]); i += 2; } else if (argv[i][0] == 'N') //print total tiems { cout << ip_uri_store.totalitems() << endl; } else { cout << "command error\n"; return 0; } } return (0); }

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  • Declaring an array of linked list in C#

    - by xarzu
    I got the compile error message "Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)" when I tried to declare an array of linked lists. public LinkedList[2] ExistingXMLList; Also, if I wanted to create a small array of strings, isn't this the way: string [2] inputdata;

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  • linked list elements gone?

    - by Hristo
    I create a linked list dynamically and initialize the first node in main(), and I add to the list every time I spawn a worker process. Before the worker process exits, I print the list. Also, I print the list inside my sigchld signal handler. in main(): head = NULL; tail = NULL; // linked list to keep track of worker process dll_node_t *node; node = (dll_node_t *) malloc(sizeof(dll_node_t)); // initialize list, allocate memory append_node(node); node->pid = mainPID; // the first node is the MAIN process node->type = MAIN; in a fork()'d process: // add to list dll_node_t *node; node = (dll_node_t *) malloc(sizeof(dll_node_t)); append_node(node); node->pid = mmapFileWorkerStats->childPID; node->workerFileName = mmapFileWorkerStats->workerFileName; node->type = WORK; functions: void append_node(dll_node_t *nodeToAppend) { /* * append param node to end of list */ // if the list is empty if (head == NULL) { // create the first/head node head = nodeToAppend; nodeToAppend->prev = NULL; } else { tail->next = nodeToAppend; nodeToAppend->prev = tail; } // fix the tail to point to the new node tail = nodeToAppend; nodeToAppend->next = NULL; } finally... the signal handler: void chld_signalHandler() { dll_node_t *temp1 = head; while (temp1 != NULL) { printf("2. node's pid: %d\n", temp1->pid); temp1 = temp1->next; } int termChildPID = waitpid(-1, NULL, WNOHANG); dll_node_t *temp = head; while (temp != NULL) { if (temp->pid == termChildPID) { printf("found process: %d\n", temp->pid); } temp = temp->next; } return; } Is it true that upon the worker process exiting, the SIGCHLD signal handler is triggered? If so, that would mean that after I print the tree before exiting, the next thing I do is in the signal handler which is print the tree... which would mean i would print the tree twice? But the tree isn't the same. The node I add in the worker process doesn't exist when I print in the signal handler or at the very end of main(). Any idea why? Thanks, Hristo

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  • sorting a doubly linked list with merge sort.

    - by user329820
    Hi I have found this code in the internet and it was for arrays ,I want to change it for doubly linked list(instead of index we should use pointer) would you please help me that how can i change merge method(I have changed sort method by myself) also this is not my home work ,I love working with linked list!! public class MergeSort { private DoublyLinkedList LocalDoublyLinkedList; public MergeSort(DoublyLinkedList list) { LocalDoublyLinkedList = list; } public void sort() { if (LocalDoublyLinkedList.size() <= 1) { return; } DoublyLinkedList listOne = new DoublyLinkedList(); DoublyLinkedList listTwo = new DoublyLinkedList(); for (int x = 0; x < (LocalDoublyLinkedList.size() / 2); x++) { listOne.add(x, LocalDoublyLinkedList.getValue(x)); } for (int x = (LocalDoublyLinkedList.size() / 2) + 1; x < LocalDoublyLinkedList.size`(); x++) {` listTwo.add(x, LocalDoublyLinkedList.getValue(x)); } //Split the DoublyLinkedList again MergeSort sort1 = new MergeSort(listOne); MergeSort sort2 = new MergeSort(listTwo); sort1.sort(); sort2.sort(); merge(listOne, listTwo); } private void merge(DoublyLinkedList a, DoublyLinkedList b) { int x = 0; int y = 0; int z = 0; while (x < first.length && y < second.length) { if (first[x] < second[y]) { a[z] = first[x]; x++; } else { a[z] = second[y]; y++; } z++; } //copy remaining elements to the tail of a[]; for (int i = x; i < first.length; i++) { a[z] = first[i]; z++; } for (int i = y; i < second.length; i++) { a[z] = second[i]; z++; } } }

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  • Generic linked list in c++

    - by itsaboy
    I have been struggling for too long a time now with a rather simple question about how to create a generic linked list in c++. The list should be able contain several types of structs, but each list will only contain one type of struct. The problem arises when I want to implement the getNode() function [see below], because then I have to specify which of the structs it should return. I have tried to substitute the structs with classes, where the getNode function returns a base class that is inherited by all the other classes, but it still does not do the trick, since the compiler does not allow the getNode function to return anything but the base class then. So here is some code snippet: typedef struct struct1 { int param1; (...) } struct1; typedef struct struct2 { double param1; (...) } struct2; typedef struct node { struct1 data; node* link; } node; class LinkedList { public: node *first; int nbrOfNodes; LinkedList(); void addNode(struct1); struct1 getNode(); bool isEmpty(); }; LinkedList::LinkedList() { first = NULL; nbrOfNodes = 0; } void LinkedList::addNode(struct1 newData) { if (nbrOfNodes == 0) { first = new node; first->data = newData; } else { node *it = first; for (int i = 0; i < nbrOfNodes; i++) { it = it->link; } node *newNode = new node; newNode->data = newData; it->link = newNode; } nbrOfNodes++; } bool LinkedList::isEmpty() { return !nbrOfNodes; } struct1 LinkedList::getNode() { param1 returnData = first->data; node* deleteNode = first; nbrOfNodes--; if (nbrOfNodes) first = deleteNode->link; delete deleteNode; return returnData; } So the question, put in one sentence, is as follows: How do I adjust the above linked list class so that it can also be used for struct2, without having to create a new almost identical list class for struct2 objects? As I said above, each instance of LinkedList will only deal with either struct1 or struct2. Grateful for hints or help

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  • reverse a linked list?

    - by sil3nt
    Hi there, Im trying to reverse the order of the following linked list, I've done so, But the reversed list does not seem to print out. Where have I gone wrong? //reverse the linked list #include <iostream> using namespace std; struct node{ int number; node *next; }; node *A; void addNode(node *&listpointer, int num){ node *temp; temp = new node; temp->number = num; temp->next = listpointer; listpointer = temp; } void reverseNode(node *&listpointer){ node *temp,*current; current = listpointer; temp = new node; while (true){ if (current == NULL){ temp = NULL; break; } temp->number = current->number; current = current->next; temp = temp->next; } listpointer = temp; } int main(){ A = NULL; addNode(A,1); addNode(A,2); addNode(A,3); while (true){ if (A == NULL){break;} cout<< A->number << endl; A = A->next; } cout<< "****" << endl; reverseNode(A); while (true){ if (A == NULL){break;} cout<< A->number << endl; A = A->next; } cout<< "****"<< endl; return 0; }

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  • C++ stl collections or linked lists

    - by Lucas
    I'm developing a OpenGL based simulation in C++. I'm optmizing my code now and i see throughout the code the frequently use of std:list and std:vector. What is the more performatic: to continue using C++ stl data structs or a pointer based linked list? The main operation that involve std::list and std::vector is open a iterator and loop through all items in the data structs and apply some processing

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  • linked-list interview question

    - by giri
    Hi This was the question asked in interview.Can anybody help me out it in implementing in java Given 2 linked lists(which need not have unique elements) find intersection point in the form of Y.(it can be anywhere--middle or tail)

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  • If tables are so evil, why does joomla use tables for its layout?

    - by DMin
    When you create a template you don't use tables. but when joomla rendereds the page, there are at least 4 places where tables are used to structure the content. Does this tell you something about tables or the fact that the joomla community should invest more time and learn how to code css or just the fact that tables are needed when you don't know what css is going to be throw in later(which probably means they are of some use)?

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