Linked List. // create a pointer to the head of the linked list // initially the list is empty.

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1 Linked List 1. Linked List A linked list is a series of connected nodes, where each node is a data structure. The nodes are dynamically allocated, used, and then deleted, allowing the linked list to grow or shrink in size as the program runs. 2. The Basic (non-class) Version The linked list header file struct ListNode { int data; ListNode *next; ; The main program #include <iostream> #include "Linked List.h" using namespace std; void main () { ListNode *head; head = NULL; ListNode *ptr; // create a pointer to the head of the linked list // initially the list is empty. // for pointing to a new node // create first new node ptr = new ListNode; // allocate memory for new node ptr >data = 7; // put data in new node ptr >next = NULL; // new node is end of the list // set head to point to this new node // create second new node ptr = new ListNode; // allocate memory for new node ptr >data = 3; // put data in new node ptr >next = head; // link previous node after this node // insert new node at beginning of the list ptr = head; printf("\n"); while(ptr!= NULL){ cout << ptr >data << endl; ptr = ptr >next; system("pause"); Page 1 of 7 Copyright Enoch Hwang 2010

2 Sample output: 3 7 Page 2 of 7 Copyright Enoch Hwang 2010

3 3. Class Version The linked list header file /* * LinkedList.h * an implementation of the linked list * * Created by Enoch Hwang on 2/1/10. * Copyright All rights reserved. * */ #ifndef LINKEDLIST #define LINKEDLIST #include <iostream> using namespace std; class LinkedList{ private: struct ListNode { int data; ListNode *next; ; ListNode *head; public: LinkedList(); void InsertNode(int d); void PrintList(); int DeleteNode(int d); ; #endif Page 3 of 7 Copyright Enoch Hwang 2010

4 The linked list definition file #include "Linked List.h" LinkedList::LinkedList(){ head = NULL; void LinkedList::InsertNode(int d){ ListNode *ptr = new ListNode; ptr >data = d; if(head == NULL){ ptr >next = NULL; else{ ptr >next = head; // allocate memory for new node // put data in new node // if list is empty // set head to point to this new node // otherwise // insert new node at beginning of the list void LinkedList::PrintList(){ ListNode *ptr = head; cout << "" << endl; while(ptr!= NULL){ cout << " " << ptr >data; ptr = ptr >next; cout << endl << endl; int LinkedList::DeleteNode(int d){ ListNode *ptr = head; ListNode *previous; // trailing pointer // need to treat the first node differently if(head >data == d){ // is the first node the one to delete? ptr = head; // yes head = head >next; delete ptr; return 1; else{ // no, then traverse list to find node to delete while((ptr!= NULL) && (ptr >data!= d)){ previous = ptr; // remember the previous node in the list ptr = ptr >next; // next node in list if(ptr){ // if node is found then delete it previous >next = ptr >next; // adjust pointer of previous node delete ptr; // release memory occupied by node return 1; else return 0; Page 4 of 7 Copyright Enoch Hwang 2010

5 The main program /* * This program demonstrates the creation of a linked list * * Created by Enoch Hwang on 2/1/10. * Copyright All rights reserved. */ #include <iostream> #include "Linked List.h" using namespace std; void main (int argc, char * const argv[]) { LinkedList L; // create an empty list cout << "Inserting node 6..." << endl; L.InsertNode(6); cout << "Inserting node 4..." << endl; L.InsertNode(4); cout << "Inserting node 8..." << endl; L.InsertNode(8); cout << "Deleting node 3..." << endl; if(l.deletenode(3)) cout << "Node deleted" << endl; else cout << "Node not deleted" << endl; cout << endl << "Deleting node 4..." << endl; if(l.deletenode(4)) cout << "Node deleted" << endl; else cout << "Node not deleted" << endl; cout << "Deleting node 8..." << endl; L.DeleteNode(8); cout << "Deleting node 6..." << endl; L.DeleteNode(6); system("pause"); Page 5 of 7 Copyright Enoch Hwang 2010

6 Sample output: Inserting node 6... Inserting node 4... Inserting node Deleting node 3... Node not deleted Deleting node 4... Node deleted 8 6 Deleting node Deleting node 6... Page 6 of 7 Copyright Enoch Hwang 2010

7 4. Exercise 1) Try out the non-class version of the linked list program. Make sure you understand the code. 2) Try out the class version of the linked list program. Make sure you understand the code. 3) Modify the class version of the linked list program so that the numbers added into the list are in ascending order when you traverse the list. In other words, when you traverse the linked list from the beginning to the end and print out each data item, the numbers printed out are in ascending order. Hint: you only need to modify the code in the InsertNode routine. 4) Add a sentinel for doing the search. 5) Create a doubly-linked list. 6) Display a menu with the options: 1) add a new node; 2) delete a node; 3) print out the entire linked list; and 0) end. Call the appropriate linked list class function to perform the selected operation. Page 7 of 7 Copyright Enoch Hwang 2010

An Incomplete C++ Primer. University of Wyoming MA 5310

An Incomplete C++ Primer. University of Wyoming MA 5310 An Incomplete C++ Primer University of Wyoming MA 5310 Professor Craig C. Douglas http://www.mgnet.org/~douglas/classes/na-sc/notes/c++primer.pdf C++ is a legacy programming language, as is other languages