Data-Structure-Algorithm/QueueUsingLinkedList.cpp at main · aruncode49/Data-Structure-Algorithm · GitHub

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#include<iostream>
#include<stdio.h>

#defineQUEUE_UNDERFLOW1;

usingnamespacestd;

structnode
{
int item;
 node *next;
};

classQueue
{
private:
 node *front; // point to start node
 node *rear; // point to last node

public:
Queue();
Queue(Queue &);
 Queue &operator=(Queue &);
voidinsertElement(int);
intgetRear();
intgetFront();
voiddeleteFront();
intcountElement();
~Queue();
};

Queue::Queue() // initially both node pointers containing null;
{
 front = rear = NULL;
}

Queue::Queue(Queue &q)
{
 front = rear = NULL;
 node *r = q.front;
while (r != NULL)
 {
insertElement(r->item);
 r = r->next;
 }
}

Queue &Queue::operator=(Queue &q)
{
while (front)
deleteFront();
 node *r = q.front;
while (r != NULL)
 {
insertElement(r->item);
 r = r->next;
 }
return *this;
}

voidQueue::insertElement(int data)
{
 node *n = new node; // prepare node
 n->item = data;
 n->next = NULL;

if (front == NULL) // if linked List is empty
 {
 front = n;
 rear = n;
 }
else// if linked list has one element or more
 {
 rear->next = n;
 rear = n;
 }
}

intQueue::getRear()
{
if (rear == NULL)
throwQUEUE_UNDERFLOW;
return rear->item;
}

intQueue::getFront()
{
if (front == NULL)
throwQUEUE_UNDERFLOW;
return front->item;
}

voidQueue::deleteFront()
{
if (front == NULL)
 {
throwQUEUE_UNDERFLOW;
 }
elseif (front->next == NULL) // or we can say that front == rear i.e list has only one element
 {
delete front;
 front = rear = NULL;
 }
else
 {
 node *r = front;
 front = front->next;
delete r;
 }
}

intQueue::countElement()
{
if(front==NULL)
return0;
elseif(front->next == NULL)
return1;
else
 {
 node *r = front;
int count=1;
while(r->next == NULL)
 {
 count++;
 r = r->next;
 }
return count;
 }
}

Queue::~Queue()
{
while (front)
deleteFront();
}