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Analogies Using Concept of Queues

A queue is a first-in, first-out (FIFO) data structure where elements are added to the rear and removed from the front. Queues can be implemented using arrays or linked lists. Circular queues were created to fully use the queue by connecting the front and rear when one reaches the end. Elements are inserted at the rear and deleted from the front, with the front pointer incrementing for deletion and rear for insertion.

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96 views3 pages

Analogies Using Concept of Queues

A queue is a first-in, first-out (FIFO) data structure where elements are added to the rear and removed from the front. Queues can be implemented using arrays or linked lists. Circular queues were created to fully use the queue by connecting the front and rear when one reaches the end. Elements are inserted at the rear and deleted from the front, with the front pointer incrementing for deletion and rear for insertion.

Uploaded by

rajanikanth
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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A queue is a FIFO (First-In, First-Out) data structure in which the element that is

inserted first is the first one to be taken out. The elements in a queue are added at one end called
the REAR and removed from the other end called the FRONT.
Analogies using concept of queues.
People waiting for a bus. The first person standing in the line will be the first one to get
into the bus.

Cars lined at a toll bridge. The first car to reach the bridge will be the first to leave.

Taking a Tickets in the Cinema Theater Queue. The First Person will collect the Ticket
and enter into the Hall.

Implementation of Queues

Queues can be implemented by using either arrays or linked lists.

IMP: the problem with queues is that unless the queue is made fully empty, we cannot use the
queue fully. To overcome this problem circular queues logic is implemented.

---------------------------------------------------------------------------------------------------------
Algorithm :

procedure qInsert(element)
//insert item into the queue represented in Q(l:n)//
if rear = MAX-1 then // if queue is full
call QUEUE_FULL;
Else // queue is not full
rear  rear + 1; //forward rear pointer by 1.
Q(rear)element; // store element at rear end
End If;
End ADDQ;

procedure qDelete()
//delete an element from queue
if front=-1 and rear=-1 then //if queue empty
call Queue is Empty;
else if front==rear //if rear and front both are equal
set rear =-1 and front=-1
else //if queue is not empty
front<-front+1; //forward front pointer by 1
End if;
end Dequeue;

import java.util.Scanner;

class Queue1{

int que[],front,rear;
Queue1(){
que=new int[5];
front=rear=0;
}

void qInsert(int no) {


if(front==0 && rear==5 ){
System.out.println("que is full");
}
else{
System.out.println("inserting "+no);
que[rear]=no;
rear++;
}
}

void qDelete() {
if(front != rear ){
System.out.println("deleting "+que[front]);
front++;
}
else{
System.out.println("Queue is empty");
front=rear=0;

}
}
void disp() {
for(int i=front;i<rear;i++)
System.out.print(que[i]+" ");
System.out.println();

}
}
public class MyQue {
public static void main(String[] args) {
Queue1 q=new Queue1();
q.qInsert(1);
q.qInsert(2);
q.qInsert(3);
q.qInsert(4);
q.qInsert(5);
q.disp();
q.qInsert(6);
q.qDelete();
q.qDelete();
q.disp();
}
}

---------------------------------------------------------------------------------------------------------

Output :

inserting 1
inserting 2
inserting 3
inserting 4
inserting 5
1 2 3 4 5
que is full
deleting 1
deleting 2
3 4 5

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