similar to a "class" concept; however, the members of the structure are by default public while the members of a class are by default private.
The difference is purely about the default access specifier.
structs are more commonly used for defining nodes in a linked list, rather than a class due to simplicity, clarity and direct access to the node's members (info & next)
classes are better used for complex behavior or encapsulation, like making the data and next members private and providing getter/setter functions, or if you want to integrate the node into a larger object-oriented design
LINKED LIST
a collection of components (aka nodes)
linked list is not similar to array; they are complex objects called nodes
in an array, the elements have positions; however, in linked list, there are no positions - it simply have elements related together using the pointer "next"
every node (except the last node) contains the address of the next node (a pointer to the next node)
every node has two components
data to store the relevant information
a link to point to the next node
ABSTRACT DATA TYPES
a type (or class) for objects whose behavior is defined by a set of values & a set of operations
the definition of ADT only mentions what operations are to be performed, but not how these operations will be implemented
TRAVERSING LINKED LIST
define a temporary pointer (current) initialized to the value of the pointer selfFirst
if you have a linked list of many nodes, where each node is pointing to the next and the last node is null.
"selfFirst" will always point to the first node
current will print the information where its currently at and then moves to the next node and print its value
DESTROYLIST()
DELETENODE()
IMPLEMENTATION
UML
VISUALIZATION
SOURCE CODE
HEADER FILE: linkedList.h
#include <assert.h>
template <class Type>
struct Node
{
Type info;
Node<Type> *next;
};
template <class Type>
class LinkedList
{
protected:
//selfLength stores the number of nodes in the Linked List
int selfLength;
//selfFirst points to the first node in the Linked List
Node<Type>* selfFirst; // "cout << selfFirst" will print the memory location where selfFirst is stored
// "cout << first->info" will print the actual data value
// the "->" symbol is used to access the fields of each node!
//selfLast points to the last node in the Linked List
Node<Type>* selfLast;
public:
LinkedList(); //constructor
bool isEmpty(); //checks whether the linked list is empty
int listSize(); //returns the number of nodes
const void print(); //displays the information inside the nodes
Type front(); //returns the information of the first node
Type back(); //returns the information of the last node
void insertFirst(const Type&); //insert a node at the beginning of the linked list
void insertLast(const Type&); //insert a node at the end of the linked list
bool search(const Type&); //searches for elements in the linked list
void deleteNode(const Type&); //searches for the specified element/node and deletes it from the linked list
LinkedList(const LinkedList<Type>&); //copy constructor; copies the list
void destroyList();
~LinkedList(); //destructor - deletes and deallocates the memory occupied by the linked list
};
//CONSTRUCTOR
template<class Type>
LinkedList<Type>::LinkedList(){
// will store the number of nodes in the Linked List
selfLength = 0;
// will point to the first node in the Linked List
selfFirst = NULL;
// will point to the last node in the Linked List
selfLast = NULL;
}
//ISEMPTY()
//returns true if the list is empty or false otherwise
template <class Type>
bool LinkedList<Type>::isEmpty(){
return selfLength == 0;
//return first == NULL; or return last == NULL
}
//LISTSIZE()
//returns the number of nodes stored in the list
template <class Type>
int LinkedList<Type>::listSize(){
return selfLength;
}
//prints the different nodes of the linked list
template <class Type>
const void LinkedList<Type>::print(){
if (isEmpty())
cout << "The list is empty, nothing to print.\n";
else{
//see TRAVERSING LINKED LIST in the Definitions section
//
Node<Type>* current = selfFirst;
while (current != NULL){
cout << current->info << " ";
current = current->next;
}
cout << "\n";
}
}
//returns the information of the first node
//FRONT()
template <class Type>
Type LinkedList<Type>::front(){
//the assert function is used to check whether the list is empty or not
//if assert() determines that the list is empty it will stop program execution
//if assert() determines that the list is NOT empty, it will return information on the first node
assert(selfFirst != NULL);
return selfFirst->info
}
//returns the information of the last node
//BACK()
Type LinkedList<Type>::back(){
//the assert function is used to check whether the list is empty or not
//if assert() determines that the list is empty it will stop program execution
//if assert() determines that the list is NOT empty, it will return information on the first node
assert(selfFirst != NULL);
return selfLast->info;
}
/*The member function insertFirst inserts the new item at the beginning of the list.
*The Algorithm is:
* 01.Create a new node
- this is done through the example below
Node<Type>* temp;
temp = new Node<Type>; //this line is used to create the node
temp->info = x;
temp->next = NULL;
* 02.If unable to create the node, terminate the program
- this simply calls the assert() function
* 03.Store the new item in the new node
* 04.Insert the node before first
* 05.Increment count by 1
*/
template <class Type>
void LinkedList<Type>::insertFirst(const Type& x){
Node<Type>* newNode; //pointer to the new node
newNode = new Node<Type>; //this line is used to create the node
assert(newNode != NULL); //checks whether the node was created
newNode->info = x; //insert the value of x to newNode->info (think of the -> as similar to the "
newNode->next = selfFirst; //newNode->next points to the first node
selfFirst = newNode; //assign the newly created node to selfFirst
selfLength++; //increment the number of nodes in the Linked List
if (selfLast == NULL)
selfLast = newNode;
}
template <class Type>
void LinkedLinst<Type>::insertLast(const Type& x){
//these five lines of code creates a new node
Node<Type>* newNode; //pointer to the new node
newNode = new Node<Type>; //this line is used to create the node
assert(newNode != NULL); //checks whether the node was created
newNode->info = x; //insert the value of x to newNode->info (think of the -> as similar to the "dot" access operator)
newNode->next = NULL;
if (selfFirst == NULL)
selfFirst = selfLast = newNode;
else{
selfLast->next = newNode;
selfLast = newNode;
}
selfLength++;
}
/*The member function search() searches for a given item. If the item is found, it
returns true, otherwise it returns false. The search must start from the first node.
- compare the search item with the current node in the list. if the info of the
current node is the same as the search item, stop the search; otherwise, make
the next node the current node.
- repeat step 1 until either the item is found or no more data is left in the
list to compare with the search item.
*/
//SEARCH()
template <class Type>
bool LinkedList<Type>::search(const Type& x){
Node<Type>* current;
bool found;
current = selfFirst;
found = false;
while (current != NULL && !found)
if (current->info == x) //this is one way to stop the loop
found = true;
else
current = current->next;
return found;
}
//deletes all nodes one after the other via loop until all nodes are deleted
//DESTROYLIST()
template <class Type>
void LinkedList<Type>::destroyList(){
Node<Type>* current;
while (selfFirst != NULL){
current = selfFirst;
selfFirst = selfFirst->next;
delete currrent;
}
selfLast = NULL;
selfLength = 0;
}
//DESTRUCTOR
template <class Type>
LinkeList<Type>::~LinkedList(){
cout << "The list was destroyed\n";
destroyList();
}
//makes a copy of a Linked List into another Linked List
//COPY CONSTRUCTOR
template <class Type>
LinkedList<Type>::LinkedList(const LinkedList<Type>& otherList){
Node<Type>* current; //pointer to traverse the otherList
if (selfFirst != NULL)
destroyList();
current = otherList.selfFirst;
while (current != NULL){
insertLast(current->info);
current = current->next;
}
selfLength = otherList.selfLength;
}
/*if the list is empty
print(can't delete from an empty list)
else if the first node is the node w/ the given info,
adjust first, last(if necessary), length, and deallocate the memory
else
search the list for the node w/ the given info
if such a node is found, delete it & adjust the values of last (if necessary), and length
*/
//DELETENODE()
template<class Type>
void LinkedList<Type>::deleteNode(const Type& x)
{
if (isEmpty())
cout << "Empty linked list. No node to be deleted\n";
else { // The linked list is not empty
//this *prevCurrent is required IOT move through the search
Node<Type>* current, *prevCurrent;
current = selfFirst;
prevCurrent = NULL;
// this iterates through the Linked List until "x" is found
// when "x" is found then use comparison starting w/ 1st if
while (current != NULL && current->info != x) {
prevCurrent = current;
current = current->next;
}
// when "x" is found then use comparison starting w/ 1st if
if (current == NULL)
cout << x <<" was not found in the linked list\n";
else { // the linked list is not empty and x was found.
if { (selfFirst == selfLast)//Linked list with only one node with info = x
delete current;
selfFirst = NULL;
selfLast = NULL;
}
else if (current == selfFirst) { //A list with more than one node and the first node has info = x
selfFirst = selfFirst->next;
delete current;
}
else if (current == selfLast) {//A list with more than one node and only the last node has info = x
selfLast = prevCurrent;
selfLast->next = NULL;
delete current;
}
else {//The node to be deleted is after first and before last
prevCurrent->next = current->next;
delete current;
}
// this shortens the length of the Link List since one of the item was deleted
selfLength--;
}
}
}
SOURCE FILE: implementation.cpp
#include<iostream>
using namespace std;
#include"LinkedList.h"
int main()
{
LinkedList<int> list; //create a list w/ default values as set by the constructor
list.insertFirst(10);
list.print();//10
list.deleteNode(10);
list.print();//Empty list
list.insertFirst(10);
list.insertFirst(20);
list.insertFirst(30);
list.insertFirst(40);
list.print();//40 30 20 10
list.deleteNode(40);
list.print();//30 20 10
LinkedList<int> list2(list);
list2.print();
cout << list2.search(20)<<"\n";
}
/*
//cout << list.front() << "\n";//40
cout << list.isEmpty() << "\n"; //0
cout << list.listSize() << "\n";//4
list.print();//40 30 20 10
list.insertLast(-1);
list.print();//40 30 20 10 -1
cout << list.search(100) << "\n"; //0
list.destroyList();*/
