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  • Display problem after deletion in linked list in C

    - by LuckySlevin
    Hi, actually this was another problem but it changed so I decided to open a new question. My code is typedef struct inner_list { int count; char word[100]; inner_list*next; } inner_list; typedef struct outer_list { char word [100]; inner_list * head; int count; outer_list * next; } outer_list; void delnode(outer_list **head,char num[100])//thanks to both Nir Levy and Jeremy P. { outer_list *temp, *m; m=temp=*head; /*FIX #1*/ while(temp!=NULL) { if(strcmp(temp->word,num)==0) { if(temp==*head) { delinner(temp->head); /* FIX#2 */ *head=temp->next; free(temp); return; } else { delinner(temp->head); /* FIX#2 */ m->next=temp->next; free(temp); return; } } else { m=temp; temp= temp->next; } } printf(" ELEMENT %s NOT FOUND ", num); } void delinner(inner_list *head) { /* FIX#2 */ inner_list *temp; temp=head; while(temp!=NULL) { head=temp->next; free(temp); temp=head; } } void delnode2(outer_list *up,inner_list **head,char num[100]) { inner_list *temp2,*temp, *m; outer_list *p; p = up; while(p!=NULL){m=temp=temp2=p->head; while(temp!=NULL) { if(strcmp(temp->word,num)==0) { if(temp==(*head)) { *head=temp->next; free(temp); return; } else { m->next=temp->next; free(temp); return; } } else { m=temp; temp= temp->next; } } p=p->next; } printf(" ELEMENT %s NOT FOUND ", num); } void print_node(outer_list *parent_node) { while(parent_node!=NULL){ printf("%s\t%d\t", parent_node->word, parent_node->count); inner_list *child_node = parent_node->head; printf("list: "); if(child_node ==NULL){printf("BUARADA");} while (child_node != NULL) { printf("%s-%d", child_node->word,child_node->count); child_node = child_node->next; if (child_node != NULL) { printf("->"); } } printf("\n"); parent_node = parent_node->next; } } While deleting an element from outer list I am also trying the delete the same element from inner_list too. For example: - Let's say aaa is an element of outer_list linked list and let's point it with outer_list *p - This aaa can also be in an inner_list linked list too. (it can be in p-head or another innerlist.) Now, the tricky part again. I tried to apply the same rules with outer_list deletion but whenever i delete the head element of inner_list it gives an error. Where is the wrong thing in print_node or delnode2?

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  • Counting number of times an item occurs in a linked list

    - by HanaCHaN92
    Here is the assignment: Here's the assignment: Implement a method countValue() that counts the number of times an item occurs in a linked list. Remember to use the STL list. int countValue(list front, const int item); Generate 20 random numbers in the range of 0 to 4, and insert each number in the linked list. Output the list by using a method which you would call writeLinkedList which you would add to the ListP.cpp. In a loop, call the method countValue() , and display the number of occurrences of each value from 0 to 4 in the list. Remember that all the above is to be included in the file ListP.ccp Run: 2 3 4 0 1 0 2 4 2 3 3 4 3 3 3 0 0 2 0 2 0 : 5, 1 : 1, 2 : 5, 3 : 6, 4 : 3 and here is what I have so far: #include<iostream> #include<list> #include<tchar.h> int countValue(list<int> front, const int item); using namespace std; int _tmain(int argc, _TCHAR* argv[]){ list<int> front; int listCount; cout << "Enter the size of the list: "; cin >> listCount; for (int i = 1; i <= listCount; i++) front.insert(rand()%5); cout << "Original List of Values: " << endl; //writeLinkedList(front, " "); cout << endl; for(int j=0;j<5;++j) cout << countValue (front,j) << endl; cout << endl; return 0; } int countValue(list<int> front, const int item) { int count0; int count1; int count2; int count3; int count4; list<int> *List; for(list<int>::iterator i = front.begin(); i != front.end(); i++) { if(List->item == 0) { count0++; } if(List->item == 1) { count1++; } if(List->item == 2) { count2++; } if(List->item == 3) { count2++; }if(List->item == 4) { count4++; } } } And here are the errors: error C2065: 'list' : undeclared identifier line 5 error C2062: type 'int' unexpected line 5 error C2661: 'std::list<_Ty>::insert' : no overloaded function takes 1 arguments line 16 error C3861: 'countValue': identifier not found line 21 IntelliSense: no instance of overloaded function "std::list<_Ty, _Ax>::insert [with _Ty=int, _Ax=std::allocator<int>]" matches the argument list line 16 IntelliSense: too few arguments in function call line 16 error C2039: 'item': is not a member of 'std::list<_Ty>' lines 34, 38, 42, 46, 49 IntelliSense: declaration is incompatible with "int countValue" (declared at line 5) line 25 IntelliSense: class "std::list<int, std:: allocator<int>>" has no member "item" lines 34, 38, 42, 46, 49 I just want to know what I've done wrong and how to fix it and also if someone could help me figure out if I'm doing the countValue function wrong or not based on the instructions I would really appreciate it. I've read the chapter in our textbook several times, looked up tutorials on youtube and on Dream in Code, and still I can not figure this out. All helpful information is appreciated!

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  • retrieve data from multiple tables referencing some tables in mysql

    - by I Like PHP
    i have 10 tables have innoDB engine 1. one is state_table which attributes are state_id and state_name 2. another table city_table which attributes are city_id and city_name 3. one more table permit_table which attribute is p_id above city_id,state_id and permit_id is references to rest of 7 tables. each table having state_id, city_id and permit_id referencing above tables now i want to extract all tables data with their respective city name and state name ( each tables may have different city id and state id) i m using below mysql query( i know it's very length way.... ) . please tell me how to do it with optimized method? SELECT p.*,cp.city_name,sp.state_name, o.*,co.city_name,so.state_name, t.*,ct.city_name,st.state_name, th.*,cth.city_name,sth.state_name, f.*,cf.city_name,sf.state_name .......so on................ .......so on................ ............................ FROM permit_table p JOIN table_city cp ON cp.city_id=p.city_id JOIN table_state sp ON sp.state_id=p.state_id JOIN table_one o ON o.permit_id=p.permit_id JOIN table_city co ON co.city_id=o.city_id JOIN table_state so ON so.state_id=o.state_id JOIN table_two t ON t.permit_id=p.permit_id JOIN table_city ct ON ct.city_id=t.city_id JOIN table_state st ON st.state_id=t.state_id JOIN table_three th ON th.permit_id=p.permit_id JOIN table_city cth ON cth.city_id=th.city_id JOIN table_state sth ON sth.state_id=th.state_id JOIN table_four f ON f.permit_id=p.permit_id JOIN table_city cf ON cf.city_id=f.city_id JOIN table_state sf ON sf.state_id=f.state_id ................so on......................... ................so on......................... .............................................. WHERE p.permit_id=base64_encode(mysql_real_escape_string($_GET[pid])); Thanks For help me always.

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  • retrive data from multiple tables referencing some tables in mysql

    - by I Like PHP
    i have 10 tables have innoDB engine 1. one is state_table which attributes are state_id and state_name 2. another table city_table which attributes are city_id and city_name 3. one more table permit_table which attribute is p_id above city_id,state_id and permit_id is references to rest of 7 tables. each table having state_id, city_id and permit_id referencing above tables now i want to extract all tables data with their respective city name and state name ( each tables may have different city id and state id) i m using below mysql query( i know it's very length way.... ) . please tell me how to do it with optimized method? SELECT p.*,cp.city_name,sp.state_name, o.*,co.city_name,so.state_name, t.*,ct.city_name,st.state_name, th.*,cth.city_name,sth.state_name, f.*,cf.city_name,sf.state_name .......so on................ .......so on................ ............................ FROM permit_table p JOIN table_city cp ON cp.city_id=p.city_id JOIN table_state sp ON sp.state_id=p.state_id JOIN table_one o ON o.permit_id=p.permit_id JOIN table_city co ON co.city_id=o.city_id JOIN table_state so ON so.state_id=o.state_id JOIN table_two t ON t.permit_id=p.permit_id JOIN table_city ct ON ct.city_id=t.city_id JOIN table_state st ON st.state_id=t.state_id JOIN table_three th ON th.permit_id=p.permit_id JOIN table_city cth ON cth.city_id=th.city_id JOIN table_state sth ON sth.state_id=th.state_id JOIN table_four f ON f.permit_id=p.permit_id JOIN table_city cf ON cf.city_id=f.city_id JOIN table_state sf ON sf.state_id=f.state_id ................so on......................... ................so on......................... .............................................. WHERE p.permit_id=base64_encode(mysql_real_escape_string($_GET[pid]); Thanks For help me always.

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  • Algorithm to create a linked list from a set of nodes

    - by user320587
    Hi, I am looking for an algorithm to create a linked list from a set of nodes. For example, let's assume a node is an airline ticket from a source point to destination. (e.g., Chicago to Detroit) and there are several airline tickets. Assuming all these airline tickets are jumbled, what is the best way to determine the entire journey path. If there are 5 airline tickets like Chicago-Detroit, Denver-Chicago, Detroit-DC, DC-New York, San Jose-Denver, the algorithm should be able to come up with the correct start to end path. San Jose - Denver - Chicago - Detroit - DC - New York

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  • Search algorithm for a sorted double linked list

    - by SalamiArmi
    As a learning excercise, I've just had an attempt at implementing my own 'merge sort' algorithm. I did this on an std::list, which apparently already had the functions sort() and merge() built in. However, I'm planning on moving this over to a linked list of my own making, so the implementation is not particuarly important. The problem lies with the fact that a std::list doesnt have facilities for accessing random nodes, only accessing the front/back and stepping through. I was originally planning on somehow performing a simple binary search through this list, and finding my answer in a few steps. The fact that there are already built in functions in an std::list for performing these kinds of ordering leads me to believe that there is an equally easy way to access the list in the way I want. Anyway, thanks for your help in advance!

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  • n elements in singly linked list

    - by Codenotguru
    The following function is trying to find the nth to last element of a singly linked list. for ex: if the elements are 8-10-5-7-2-1-5-4-10-10 then the result is 7th to last node is 7. Can anybody help me on how this code is working or is there a better and simpler approach? LinkedListNode nthToLast(LinkedListNode head, int n) { if (head == null || n < 1) { return null; } LinkedListNode p1 = head; LinkedListNode p2 = head; for (int j = 0; j < n - 1; ++j) { // skip n-1 steps ahead if (p2 == null) { return null; // not found since list size < n } p2 = p2.next; } while (p2.next != null) { p1 = p1.next; p2 = p2.next; } return p1; }

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  • Problems with Linked List in C

    - by seePhor
    Hey everyone, I am new to C and I am working on an XOR linked list for a project. I have most of the code done, but I can't seem to get the delete function of the list to work properly. It seems able to delete some numbers, but not any number you pass into the function. Could anyone experienced with C take a look and possibly point out where I went wrong? I have been working on this for a while now and have not had much luck and I have started over 3 times :( Any help is much appreciated. Thank you. You can see my first attempt of code here. I can only post one link, so if you would like to see my second attempt, just tell me so and I can email it to you or something. Thank you for your time.

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  • TStringList, Dynamic Array or Linked List in Delphi?

    - by lkessler
    I have a choice. I have an array of ordered strings that I need to store and access. It looks like I can choose between using: A TStringList A Dynamic Array of strings, and A Linked List of strings In what circumstances is each of these better than the others? Which is best for small lists (under 10 items)? Which is best for large lists (over 1000 items)? Which is best for huge lists (over 1,000,000 items)? Which is best tor minimize memory use? Which is best to minimize loading and/or access time? For reference, I am using Delphi 2009.

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  • C++ Memory Allocation & Linked List Implementation

    - by pws5068
    I'm writing software to simulate the "first-fit" memory allocation schema. Basically, I allocate a large X megabyte chunk of memory and subdivide it into blocks when chunks are requested according to the schema. I'm using a linked list called "node" as a header for each block of memory (so that we can find the next block without tediously looping through every address value. head_ptr = (char*) malloc(total_size + sizeof(node)); if(head_ptr == NULL) return -1; // Malloc Error .. :-( node* head_node = new node; // Build block header head_node->next = NULL; head_node->previous = NULL; // Header points to next block (which doesn't exist yet) memset(head_ptr,head_node, sizeof(node)); ` But this last line returns: error: invalid conversion from 'node*' to 'int' I understand why this is invalid.. but how can I place my node into the pointer location of my newly allocated memory?

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  • C++ Linked List - Reading data from a file with a sentinel

    - by Nick
    So I've done quite a bit of research on this and can't get my output to work correctly. I need to read in data from a file and have it stored into a Linked List. The while loop used should stop once it hits the $$$$$ sentinel. Then I am to display the data (by searching by ID Number[user input]) I am not that far yet I just want to properly display the data and get it read in for right now. My problem is when it displays the data is isn't stopping at the $$$$$ (even if I do "inFile.peek() != EOF and omit the $$$$$) I am still getting an extra garbage record. I know it has something to do with my while loop and how I am creating a new Node but I can't get it to work any other way. Any help would be appreciated. students.txt Nick J Cooley 324123 60 70 80 90 Jay M Hill 412254 70 80 90 100 $$$$$ assign6.h file #pragma once #include <iostream> #include <string> using namespace std; class assign6 { public: assign6(); // constructor void displayStudents(); private: struct Node { string firstName; string midIni; string lastName; int idNum; int sco1; //Test score 1 int sco2; //Test score 2 int sco3; //Test score 3 int sco4; //Test score 4 Node *next; }; Node *head; Node *headPtr; }; assign6Imp.cpp // Implementation File #include "assign6.h" #include <fstream> #include <iostream> #include <string> using namespace std; assign6::assign6() //constructor { ifstream inFile; inFile.open("students.txt"); head = NULL; head = new Node; headPtr = head; while (inFile.peek() != EOF) //reading in from file and storing in linked list { inFile >> head->firstName >> head->midIni >> head->lastName; inFile >> head->idNum; inFile >> head->sco1; inFile >> head->sco2; inFile >> head->sco3; inFile >> head->sco4; if (inFile != "$$$$$") { head->next = NULL; head->next = new Node; head = head->next; } } head->next = NULL; inFile.close(); } void assign6::displayStudents() { int average = 0; for (Node *cur = headPtr; cur != NULL; cur = cur->next) { cout << cur->firstName << " " << cur->midIni << " " << cur->lastName << endl; cout << cur->idNum << endl; average = (cur->sco1 + cur->sco2 + cur->sco3 + cur->sco4)/4; cout << cur->sco1 << " " << cur->sco2 << " " << cur->sco3 << " " << cur->sco4 << " " << "average: " << average << endl; } }

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  • recursively reverse linked list.

    - by Amanda
    I am implementing a function to recursively reverse a linked-list, but getting seg-fault. typedef struct _node { int data; struct _node *next; } Node, *NodeP; NodeP recursiveReverseList(NodeP first){ if(first == NULL) return NULL; if(first->next == NULL) return head; NodeP rest = recursiveReverseList(head->next); rest->next = first; first->next = NULL; return first; } Can you please help. P.S. The iterative version is working fine though. Its not homework. Just practicing C.

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  • Linked List. Insert integers in order

    - by user69514
    I have a linked list of integers. When I insert a new Node I need to insert it not at the end, but in oder... i.e. 2, 4, 5, 8, 11, 12, 33, 55, 58, 102, etc. I don't think I am inserting it in the correct position. Do see what Im doing wrong? Node newNode = new Node(someInt); Node current = head; for(int i=0; i<count; i++){ if(current == tail && tail.data < someInt){ tail.next = newNode; } if(current.data < someInt && current.next.data >= someInt){ newNode.next = current.next; current.next = newNode; } }

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  • Conditional jump or move depends on uninitialised value - freeing a linked list

    - by user720491
    I want to free a linked list in C. All is working fine, but Valgrind is telling me Conditional jump or move depends on uninitialised value(s) at 0x401400: mtf_destroy Here's the code: list_elt *head; void mtf_init() { list_elt *current; head = malloc(sizeof(list_elt)); current = head; for (int i = 0; i < LIST_SIZE-1; i++) { current->value = (BYTE) i; current->next = malloc(sizeof(list_elt)); current = current->next; } current->value = LIST_SIZE-1; } void mtf_destroy(list_elt *elt) { if (elt->next != NULL) mtf_destroy(elt->next); free(elt); } How can I solve this? Thanks!

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  • concurrent doubly-linked list (1 writer, n-readers)

    - by Arne
    Hi guys, I am back in the field of programming for my Diploma-thesis now and stumbled over the following issue: I need to implement a thread-safe doubly-linked list for one thread writing the list at any position (delete, insert, mutate node data) and one to many threads traversing and reading the list. I am well aware that mutexes can be used to serialize access to the list, still I presume that a naive lock around any write operation will be less than optimal. I am wondering whether there are better variants. (I am well aware that 'optimal' has not much of a practical meaning as long as no exact measure/profiling are available but this is an academic thesis after all..) I am very gratefull for code-samples as well as references to academic granted these have at least a tiny bit of practical relevance. Thanks at lot

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  • setting up linked list Java

    - by erp
    I'm working on some basic linked list stuff, like insert, delete, go to the front or end of the list, and basically i understand the concept of all of that stuff once i have the list i guess but im having trouble setting up the list. I was wondering of you guys could tell me if im going in the right direction. (mostly just the setup) this is what i have so far: public class List { private int size; private List linkedList; List head; List cur; List next; /** * Creates an empty list. * @pre * @post */ public List(){ linkedList = new List(); this.head = null; cur = head; } /** * Delete the current element from this list. The element after the deleted element becomes the new current. * If that's not possible, then the element before the deleted element becomes the new current. * If that is also not possible, then you need to recognize what state the list is in and define current accordingly. * Nothing should be done if a delete is not possible. * @pre * @post */ public void delete(){ // delete size--; } /** * Get the value of the current element. If this is not possible, throw an IllegalArgumentException. * @pre the list is not empty * @post * @return value of the current element. */ public char get(){ return getItem(cur); } /** * Go to the last element of the list. If this is not possible, don't change the cursor. * @pre * @post */ public void goLast(){ while (cur.next != null){ cur = cur.next; } } /** * Advance the cursor to the next element. If this is not possible, don't change the cursor. * @pre * @post */ public void goNext(){ if(cur.next != null){ cur = cur.next;} //else do nothing } /** * Retreat the cursor to the previous element. If this is not possible, don't change the cursor. * @pre * @post */ public void goPrev(){ } /** * Go to top of the list. This is the position before the first element. * @pre * @post */ public void goTop(){ } /** * Go to first element of the list. If this is not possible, don't change the cursor. * @pre * @post */ public void goFirst(){ } /** * Insert the given parameter after the current element. The newly inserted element becomes the current element. * @pre * @post * @param newVal : value to insert after the current element. */ public void insert(char newVal){ cur.setItem(newVal); size++; } /** * Determines if this list is empty. Empty means this list has no elements. * @pre * @post * @return true if the list is empty. */ public boolean isEmpty(){ return head == null; } /** * Determines the size of the list. The size of the list is the number of elements in the list. * @pre * @post * @return size which is the number of elements in the list. */ public int size(){ return size; } public class Node { private char item; private Node next; public Node() { } public Node(char item) { this.item = item; } public Node(char item, Node next) { this.item = item; this.next = next; } public char getItem() { return this.item; } public void setItem(char item) { this.item = item; } public Node getNext() { return this.next; } public void setNext(Node next) { this.next = next; } } } I got the node class alright (well i think it works alright), but is it necessary to even have that class? or can i go about it without even using it (just curious). And for example on the method get() in the list class can i not call that getItem() method from the node class because it's getting an error even though i thought that was the whole point for the node class. bottom line i just wanna make sure im setting up the list right. Thanks for any help guys, im new to linked list's so bear with me!

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  • Iterators over a LInked List in a Game in Java

    - by Matthew
    I am using OpenGl in android and they have a callback method called draw that gets called with out my control. (As fast as the device can handle if I am not mistaken) I have a list of "GameObjects" that have a .draw method and a .update method. I have two different threads that handle each of those. So, the question is, can I declare two different iterators in two different methods in two different threads that iterate over the same Linked List? If so, do I simply declare ListIterator<GameObject> l = objets.listIterator() each time I want a new iterator and it won't interfere with other iterators?

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  • Reversing linked list C

    - by user2976389
    node *rever(node *root) { node *prev = NULL; node *xnew = NULL; while (root != NULL) { xnew = malloc(sizeof(root)); xnew->value = root->value; xnew->next = prev; prev = xnew; root = root->next; } return xnew; } Hello I wrote this linked list reverse function. However it doesn't work(empty response): I suspect it's because of prev index getting overwritten. Could someone explain me whats going on? I know I could find working code on the internet but I wanna know what am I doing wrong. Thanks

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  • Linked List manipulation, issues retrieving data c++

    - by floatfil
    I'm trying to implement some functions to manipulate a linked list. The implementation is a template typename T and the class is 'List' which includes a 'head' pointer and also a struct: struct Node { // the node in a linked list T* data; // pointer to actual data, operations in T Node* next; // pointer to a Node }; Since it is a template, and 'T' can be any data, how do I go about checking the data of a list to see if it matches the data input into the function? The function is called 'retrieve' and takes two parameters, the data and a pointer: bool retrieve(T target, T*& ptr); // This is the prototype we need to use for the project "bool retrieve : similar to remove, but not removed from list. If there are duplicates in the list, the first one encountered is retrieved. Second parameter is unreliable if return value is false. E.g., " Employee target("duck", "donald"); success = company1.retrieve(target, oneEmployee); if (success) { cout << "Found in list: " << *oneEmployee << endl; } And the function is called like this: company4.retrieve(emp3, oneEmployee) So that when you cout *oneEmployee, you'll get the data of that pointer (in this case the data is of type Employee). (Also, this is assuming all data types have the apropriate overloaded operators) I hope this makes sense so far, but my issue is in comparing the data in the parameter and the data while going through the list. (The data types that we use all include overloads for equality operators, so oneData == twoData is valid) This is what I have so far: template <typename T> bool List<T>::retrieve(T target , T*& ptr) { List<T>::Node* dummyPtr = head; // point dummy pointer to what the list's head points to for(;;) { if (*dummyPtr->data == target) { // EDIT: it now compiles, but it breaks here and I get an Access Violation error. ptr = dummyPtr->data; // set the parameter pointer to the dummy pointer return true; // return true } else { dummyPtr = dummyPtr->next; // else, move to the next data node } } return false; } Here is the implementation for the Employee class: //-------------------------- constructor ----------------------------------- Employee::Employee(string last, string first, int id, int sal) { idNumber = (id >= 0 && id <= MAXID? id : -1); salary = (sal >= 0 ? sal : -1); lastName = last; firstName = first; } //-------------------------- destructor ------------------------------------ // Needed so that memory for strings is properly deallocated Employee::~Employee() { } //---------------------- copy constructor ----------------------------------- Employee::Employee(const Employee& E) { lastName = E.lastName; firstName = E.firstName; idNumber = E.idNumber; salary = E.salary; } //-------------------------- operator= --------------------------------------- Employee& Employee::operator=(const Employee& E) { if (&E != this) { idNumber = E.idNumber; salary = E.salary; lastName = E.lastName; firstName = E.firstName; } return *this; } //----------------------------- setData ------------------------------------ // set data from file bool Employee::setData(ifstream& inFile) { inFile >> lastName >> firstName >> idNumber >> salary; return idNumber >= 0 && idNumber <= MAXID && salary >= 0; } //------------------------------- < ---------------------------------------- // < defined by value of name bool Employee::operator<(const Employee& E) const { return lastName < E.lastName || (lastName == E.lastName && firstName < E.firstName); } //------------------------------- <= ---------------------------------------- // < defined by value of inamedNumber bool Employee::operator<=(const Employee& E) const { return *this < E || *this == E; } //------------------------------- > ---------------------------------------- // > defined by value of name bool Employee::operator>(const Employee& E) const { return lastName > E.lastName || (lastName == E.lastName && firstName > E.firstName); } //------------------------------- >= ---------------------------------------- // < defined by value of name bool Employee::operator>=(const Employee& E) const { return *this > E || *this == E; } //----------------- operator == (equality) ---------------- // if name of calling and passed object are equal, // return true, otherwise false // bool Employee::operator==(const Employee& E) const { return lastName == E.lastName && firstName == E.firstName; } //----------------- operator != (inequality) ---------------- // return opposite value of operator== bool Employee::operator!=(const Employee& E) const { return !(*this == E); } //------------------------------- << --------------------------------------- // display Employee object ostream& operator<<(ostream& output, const Employee& E) { output << setw(4) << E.idNumber << setw(7) << E.salary << " " << E.lastName << " " << E.firstName << endl; return output; } I will include a check for NULL pointer but I just want to get this working and will test it on a list that includes the data I am checking. Thanks to whoever can help and as usual, this is for a course so I don't expect or want the answer, but any tips as to what might be going wrong will help immensely!

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  • Faster way to transfer table data from linked server

    - by spender
    After much fiddling, I've managed to install the right ODBC driver and have successfully created a linked server on SQL Server 2008, by which I can access my PostgreSQL db from SQL server. I'm copying all of the data from some of the tables in the PgSQL DB into SQL Server using merge statements that take the following form: with mbRemote as ( select * from openquery(someLinkedDb,'select * from someTable') ) merge into someTable mbLocal using mbRemote on mbLocal.id=mbRemote.id when matched /*edit*/ /*clause below really speeds things up when many rows are unchanged*/ /*can you think of anything else?*/ and not (mbLocal.field1=mbRemote.field1 and mbLocal.field2=mbRemote.field2 and mbLocal.field3=mbRemote.field3 and mbLocal.field4=mbRemote.field4) /*end edit*/ then update set mbLocal.field1=mbRemote.field1, mbLocal.field2=mbRemote.field2, mbLocal.field3=mbRemote.field3, mbLocal.field4=mbRemote.field4 when not matched then insert ( id, field1, field2, field3, field4 ) values ( mbRemote.id, mbRemote.field1, mbRemote.field2, mbRemote.field3, mbRemote.field4 ) WHEN NOT MATCHED BY SOURCE then delete; After this statement completes, the local (SQL Server) copy is fully in sync with the remote (PgSQL server). A few questions about this approach: is it sane? it strikes me that an update will be run over all fields in local rows that haven't necessarily changed. The only prerequisite is that the local and remote id field match. Is there a more fine grained approach/a way of constraining the merge statment to only update rows that have actually changed?

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  • Big problem with Dijkstra algorithm in a linked list graph implementation

    - by Nazgulled
    Hi, I have my graph implemented with linked lists, for both vertices and edges and that is becoming an issue for the Dijkstra algorithm. As I said on a previous question, I'm converting this code that uses an adjacency matrix to work with my graph implementation. The problem is that when I find the minimum value I get an array index. This index would have match the vertex index if the graph vertexes were stored in an array instead. And the access to the vertex would be constant. I don't have time to change my graph implementation, but I do have an hash table, indexed by a unique number (but one that does not start at 0, it's like 100090000) which is the problem I'm having. Whenever I need, I use the modulo operator to get a number between 0 and the total number of vertices. This works fine for when I need an array index from the number, but when I need the number from the array index (to access the calculated minimum distance vertex in constant time), not so much. I tried to search for how to inverse the modulo operation, like, 100090000 mod 18000 = 10000 and, 10000 invmod 18000 = 100090000 but couldn't find a way to do it. My next alternative is to build some sort of reference array where, in the example above, arr[10000] = 100090000. That would fix the problem, but would require to loop the whole graph one more time. Do I have any better/easier solution with my current graph implementation?

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  • A queue in C using structs and dynamic memory allocation (linked list)

    - by Martin Pugh
    I am tasked with making a queue data structure in C, as a linked list. Our lecturer gave us a large amount of code to implement a stack, but we have to adapt it to create a queue. The code our lecturer gave us ends up not compiling and segfaulting at the exact same point as the code I wrote for the queue. I'm very new to structs, malloc and C in general, so there could be something painfully obvious I've overlooked. Here is the code I am using: #include <stdio.h> #include <stdlib.h> struct node{ int data; //contains the actual data struct node *prev; //pointer to previous node (Closer to front) struct node *next; //pointer to next node (Closer to back) }; typedef struct node *Nodepointer; struct queue{ Nodepointer front; Nodepointer back; }; typedef struct queue *Queuepointer; main(){ Queuepointer myqueue; //create a queue called myqueue init(myqueue); //initialise the queue Nodepointer new = (Nodepointer)malloc(sizeof(struct node)); myqueue->front = new; } int init(Queuepointer q){ q = (Queuepointer)malloc(sizeof(struct queue)); q->front = NULL; q->back = NULL; } The idea is that the queue struct 'contains' the first and last nodes in a queue, and when a node is created, myqueue is updated. However, I cannot even get to that part (pop and push are written but omitted for brevity). The code is segfaulting at the line myqueue->front = new; with the following gdb output: Program received signal SIGSEGV, Segmentation fault. 0x08048401 in main () at queue.c:27 27 myqueue->front = new; Any idea what I'm doing wrong?

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  • Linked List Sorting with Strings In C

    - by user308583
    I have a struct, with a Name and a single Node called nextName It's a Singly Linked list, and my task is to create the list, based on alphabetical order of the strings. So iff i enter Joe Zolt and Arthur i should get my list structured as Joe Than Joe Zolt Than Arthur Joe Zolt I'm having trouble implementing the correct Algorithm, which would put the pointers in the right order. This is What I have as of Now. Temp would be the name the user just entered and is trying to put into the list, namebox is just a copy of my root, being the whole list if(temp != NULL) { struct node* namebox = root; while (namebox!=NULL && (strcmp((namebox)->name,temp->name) <= 0)) { namebox = namebox->nextName; printf("here"); } temp->nextName = namebox; namebox = temp; root = namebox; This Works right now, if i enter names like CCC BBB than AAA I Get Back AAA BBB CCC when i print But if i put AAA BBB CCC , When i print i only get CCC, it cuts the previous off.

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  • sorting names in a linked list

    - by sil3nt
    Hi there, I'm trying to sort names into alphabetical order inside a linked list but am getting a run time error. what have I done wrong here? #include <iostream> #include <string> using namespace std; struct node{ string name; node *next; }; node *A; void addnode(node *&listpointer,string newname){ node *temp; temp = new node; if (listpointer == NULL){ temp->name = newname; temp->next = listpointer; listpointer = temp; }else{ node *add; add = new node; while (true){ if(listpointer->name > newname){ add->name = newname; add->next = listpointer->next; break; } listpointer = listpointer->next; } } } int main(){ A = NULL; string name1 = "bob"; string name2 = "tod"; string name3 = "thomas"; string name4 = "kate"; string name5 = "alex"; string name6 = "jimmy"; addnode(A,name1); addnode(A,name2); addnode(A,name3); addnode(A,name4); addnode(A,name5); addnode(A,name6); while(true){ if(A == NULL){break;} cout<< "name is: " << A->name << endl; A = A->next; } return 0; }

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  • pointer to a pointer in a linked list

    - by user1596497
    I'm trying to set a linked list head through pointer to a pointer. I can see inside the function that the address of the head pointer is changing but as i return to the main progran it becomes NULL again. can someone tell me what I'm doing wrong ?? #include <stdio.h> #include <stdlib.h> typedef void(*fun_t)(int); typedef struct timer_t { int time; fun_t func; struct timer_t *next; }TIMER_T; void add_timer(int sec, fun_t func, TIMER_T *head); void run_timers(TIMER_T **head); void timer_func(int); int main(void) { TIMER_T *head = NULL; int time = 1; fun_t func = timer_func; while (time < 1000) { printf("\nCalling add_timer(time=%d, func=0x%x, head=0x%x)\n", time, func, &head); add_timer(time, func, head); time *= 2; } run_timers(&head); return 0; } void add_timer(int sec, fun_t func, TIMER_T *head) { TIMER_T ** ppScan=&head; TIMER_T *new_timer = NULL; new_timer = (TIMER_T*)malloc(sizeof(TIMER_T)); new_timer->time = sec; new_timer->func = func; new_timer->next = NULL; while((*ppScan != NULL) && (((**ppScan).time)<sec)) ppScan = &(*ppScan)->next; new_timer->next = *ppScan; *ppScan = new_timer; }

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