1. CSC 248 – fundamentals of Data structure
CHAPTER 4 – QUEUE
PREPARED BY : ZANARIAH IDRUS
CSC 248 – fundamentals of Data structure

2. CHAPTER OBJECTIVES Understanding Queue Operations on Queue
Applications of Queue

3. APPLICATIONS OF QUEUES
Scheduler
For controlling access to shared resources
Maintain queues for printers’ jobs
Maintains queues of disk input/output requests
Simulation of real world situations
Use queues to simulate waiting line queues in real scenarios
Public places such as bank, service counter and ticket counter (bus, train, flight-checki-n)
Telephone operators
Queuing system for handling calls to toll-free numbers

4. QUEUE Represents a waiting line.
First-in First-out (FIFO) data structure.
Nodes are removed only from the head of the queue, and are inserted only at the tail of the queue.
Insert operation is known as ENQUEUE (enQ)
Remove operation is known as DEQUEUE (deQ)

5. ENQUEUE
Insert operation is known as ENQUEUE.

6. DEQUEUE Remove operation is known as DEQUEUE.
It remove an element from the front of the queue, provided the queue is not Empty

7. OPERATIONS ON QUEUE
initializeQueue: Initializes the queue to an empty state.
isEmptyQueue: Determines whether the queue is empty. If the queue is empty, it returns the value true; otherwise, it returns the value false.
isFullQueue: Determines whether the queue is full. If the queue is full, it returns the value true; otherwise, it returns the value false.
getFront: Returns the front (first) element of the queue; the queue must exist.
back: Returns the rear (last) element of the queue; the queue must exist.
addQueue: Adds a new element to the rear of the queue; the queue must exist and must not be full.
deleteQueue: Removes the front element of the queue; the queue must exist and must not be empty.

8. OPERATIONS ON QUEUE
Searching – search a particular element in queue (check and get the elements using dequeue method
Queue must be dequeue (remove data ) in order to traverse the queue
Removed data from queue must be keep and send into temporary queue if the data need to be used again
In queue, the order of the data will not change after and inserting process using temporary queue

9. IMPLEMENTATION QUEUE AS ARRAY

10. IMPLEMENTATION QUEUE AS ARRAY

11. IMPLEMENTATION QUEUE AS LINKED LIST

12. IMPLEMENTATION QUEUE AS LINKED LIST

13. QUEUE CLASS DEFINITION
Class: Queue extends LinkedList class
Methods:
Constructors (default)
Enqueue (object) // insert element at the end of queue
Dequeue ( ) // remove element from front of queue
getFront ( ) // get the front element
getEnd ( ) // get the end element
isEmpty ( ) // check if queue is Empty (inherit from class LinkedList)

14. INITIALIZE QUEUE
public void initializeQueue() { for(int i = queueFront; i < queueRear; i = (i + 1) % maxQueueSize) list[i] = null; queueFront = 0; queueRear = maxQueueSize -1; count = 0; }

15. EMPTY QUEUE & FULLQUEUE
public boolean isEmptyQueue() { return (count == 0); } public boolean isFullQueue() return (count == maxQueueSize);

16. FRONT
public Object front() throws QueueUnderflowException { if(isEmptyQueue()) throw new QueueUnderflowException(); Object temp = list[queueFront]; return temp; }

17. BACK
public Object back() throws QueueUnderflowException { if(isEmptyQueue()) throw new QueueUnderflowException(); Object temp = list[queueRear]; return temp; }

18. ADD QUEUE
public void addQueue(Object queueElement) throws QueueOverflowException { if(isFullQueue()) throw new QueueOverflowException(); queueRear = (queueRear + 1) % maxQueueSize; //use the mod //operator to advance queueRear //because the array is circular count++; list[queueRear] = queueElement; }

19. DELETE QUEUE
public void deleteQueue() throws QueueUnderflowException { if(isEmptyQueue()) throw new QueueUnderflowException(); count--; list[queueFront] = null; queueFront = (queueFront + 1) % maxQueueSize; //use the mod //operator to advance queueFront //because the array is circular }

20. OTHERS APPLICATIONS OF QUEUE
Simulation: technique in which one system models the behavior of another system; used when it is too expensive or dangerous to experiment with real systems.
Simulationexamples:
Wind tunnels used to experiment with design of car bodies
Flight simulators used to train airline pilots
Computer simulations: objects being usually represented as data