QUEUE

In this post we will study about “QUEUE” and its application.

                                                             “QUEUE”

  • Like stack queue is a linear structure.
  • which follows a particular order in which the operations are performed.
  • The order is First In First Out (FIFO).
  •  Unlike stacks, a queue is open at both its ends.
  • One end is always used to insert data (enqueue) and the other is used to remove data (dequeue).

Examples of QUEUE:

  • examplee of queue can be a single-lane one-way road where the vehicle enters first exits first.
  • queue at the ticket windows and bus-stop.

 

 

Operations on Queue:

There are 4 type of operation performed in queue:

  1. Enqueue
  2. Dequeue
  3. Front
  4. Rear. 

 

 

ENQUEUE:

  1. The word means add an item to the queue.
  2. If the queue is full, then it is said to be an Overflow condition.

Algorithm for enqueue operation:

1. Create a new node
ptr=(qType*)malloc(sizeof(qType))

2. Assign the item to info

set ptr->info = item

3. Adjust ptr
set ptr->next= NULL

4. Check for existing queue

if ( rear==NULL)
{
set rear=ptr
set front=ptr
}

else goto 5.

5. Adjust rear pointer

Set  rear -> next =ptr
Set rear= ptr

6.exit

before enqueue

after enqueue

CODE:

 

DEQUEUE:

  • Removes an item from the queue.
  • The items are popped in the same order in which they are pushed.
  • If the queue is empty, then it is said to be an Underflow condition.

 

Algorithm for dequeue operation:

1. Check if  queue is Empty

if (front==NULL)

display “Stack Empty ” and exit else goto 2

2. Set temp=front
3. Adjust fron

front=front->next

4. Display temp->info
5.Free(temp)
6.Exit

before dequeue

after dequeue

code

 

FRONT:

  • Get the front item from queue.

Code:

 

REAR:

  • Get the last item from queue

code:

 

 

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