Page 188 - DCAP201_FUNDAMENTALS_OF_DATA_STRUCTURES

Unit 11: Operations and Applications of Queues

Check whether a queue is full (Is full): Checks whether the queue is full. (If Is full is true, Notes
then the removal of an item is possible. If this is false, then acknowledge with the message
“Queue is full”).
Add item at the rear of the queue(enqueue).
Remove item from front of queue(dequeue).

Read the front of the queue.
Print the entire queue.

Notes The primitive isEmpty(Q) is required to know whether the queue is empty or not,
because calling next on an empty queue should cause an error. Like stack, the situation
may be such when the queue is “full” in the case of a finite queue. But we avoid defining
this as it would depend on the actual length of the Queue defined in a specific problem.

Task Make distinction between is empty and Is full operation.
11.1.1 Enqueue Operation

This operation is used to add an item to the queue at the rear end. So, the head of the queue will
be now occupied with an item currently added in the queue. Head count will be incremented by
one after addition of each item until the queue reaches the tail point.

!
Caution This operation will be performed at the rear end of the queue.

The following code below will state the Enqueue operation through a function:-
1. enqueue()
2. {
3. int item;
4. if (rear==MAX-1) /* QUEUE FULL condition */
5. printf(“Queue Overflow, Cannot insert more elements\n”);
6. else
7. {
8. if (front==-1) /*If queue is initially empty */

9. front=0;
10. printf(“Enter the data element that is to be inserted in queue:”);
11. scanf(“%d”, &item);
12. rear=rear+1; /* incrementing rear for holding the index of added ele*/
13. queue[rear] = item;
14. }
15. }

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