queue & its applications
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The document discusses different types of queues including their representations, operations, and applications. It describes queues as linear data structures that follow a first-in, first-out principle. Common queue operations are insertion at the rear and deletion at the front. Queues can be represented using arrays or linked lists. Circular queues and priority queues are also described as variants that address limitations of standard queues. Real-world and technical applications of queues include CPU scheduling, cashier lines, and data transfer between processes.
![Array Representation of Queues
12 9 7 18
12 9 7 18 14
A[0] A[1] A[2] A[3] A[4]
QUEUE
front
rear
front
rearQueue after insertion of a new element
9 7 18 14
front rear
Queue after deletion of an element](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-8-320.jpg)
![Algorithm to insert an element in queue
STEP-1 IF REAR= MAX-1
write OVERFLOW
go to step 4
[end of if]
STEP-2 if REAR = -1
set FRONT=REAR= 0
else
set REAR = REAR+1
STEP-3 set QUEUE [ REAR ] = NUM
STEP-4 EXIT
INITIALLY
REAR = -1
FRONT =-1](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-9-320.jpg)
![Algorithm to delete an element from queue
STEP-1 If FRONT = -1 or FRONT > REAR
write UNDERFLOW
Else
set VAL = QUEUE [ FRONT ]
set FRONT = FRONT + 1
[end of if]
STEP-2 EXIT](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-10-320.jpg)
![Algorithm to insert an element in queue
using linked list
STEP-1 Allocate memory for the new node & name it as TEMP.
STEP-2 set TEMP data = NUM
set TEMP link = NULL
STEP-3 If FRONT = NULL
FRONT = REAR = TEMP
Else
REAR link = TEMP
REAR = TEMP
[ end of if]
STEP-4 EXIT
INITIALLY
FRONT=NULL
REAR=NULL](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-12-320.jpg)
![Algorithm to delete an element from queue
STEP-1 If FRONT = NULL
write underflow
go to step 3.
[end of if]
STEP-2 set TEMP = FRONT
FRONT = FRONT link
if FRONT = NULL
REAR = NULL
STEP-3 EXIT](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-13-320.jpg)
![Algorithm to insert an element in queue
STEP-1 If FRONT = (REAR+1)%MAX
write OVERFLOW
go to step 4
[end of if]
STEP-2 If FRONT = -1
REAR = FRONT = 0
Else REAR = (REAR +1)%MAX
[ end of if ]
STEP-3 CQ[REAR] = NUM
STEP-4 EXIT
INITIALLY
FRONT= -1
REAR= 0](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-18-320.jpg)
![Algorithm to delete an element from queue
STEP-1 If FRONT = -1
write UNDERFLOW
go to step 3
[ end of if ]
STEP-2 If FRONT = REAR
FRONT = REAR= -1
Else
FRONT = (FRONT +1)%MAX
STEP-3 EXIT](https://image.slidesharecdn.com/somendra-que-161028132228/85/queue-its-applications-19-320.jpg)
queue & its applications
- 2. Contents Introduction Operations on queue Array representation of queues Linked representation of queues Types of queues Circular queues Deques Priority queues Application of queues References
- 3. DATA STRUCTURE A data structure is a particular way of organizing data in a computer so that it can be used efficiently. Different kind of data structure suits for the different kind of applications.
- 4. Data Structure Linear Array Linked list Stack Queue Primitive DS Non-Primitive DS Non Linear Tree Graph Integer Float Char Pointers
- 5. • Queue is a linear data structure. • It is used for temporary storage of data values. • A new element is added at one end called rear end. • The existing elements deleted from the other end called front end. • First-in-First-out property. 34 12 53 61 9 23 42 front rear
- 6. Operations on Queue 1.Insertion : Placing an item in a queue is called “insertion or enqueue”, which is done at the end of the queue called “rear”. Front Rear
- 7. 2.Deletion : Removing an item from a queue is called “deletion or dequeue” , which is done at the other end of the queue called “front”. Front Rear
- 8. Array Representation of Queues 12 9 7 18 12 9 7 18 14 A[0] A[1] A[2] A[3] A[4] QUEUE front rear front rearQueue after insertion of a new element 9 7 18 14 front rear Queue after deletion of an element
- 9. Algorithm to insert an element in queue STEP-1 IF REAR= MAX-1 write OVERFLOW go to step 4 [end of if] STEP-2 if REAR = -1 set FRONT=REAR= 0 else set REAR = REAR+1 STEP-3 set QUEUE [ REAR ] = NUM STEP-4 EXIT INITIALLY REAR = -1 FRONT =-1
- 10. Algorithm to delete an element from queue STEP-1 If FRONT = -1 or FRONT > REAR write UNDERFLOW Else set VAL = QUEUE [ FRONT ] set FRONT = FRONT + 1 [end of if] STEP-2 EXIT
- 11. Linked Representation of Queues 9 300 7 350 4 360 2 N 290 Front 300 350 360 rear Linked queue 9 300 7 350 4 360 2 380 290 front 300 350 360 380 rear 5 N Linked queue after inserting a node 7 350 4 360 2 380 380 rear 5 N 300 front 350 360 Linked queue after deleting a node Front = 290 Rear = 360
- 12. Algorithm to insert an element in queue using linked list STEP-1 Allocate memory for the new node & name it as TEMP. STEP-2 set TEMP data = NUM set TEMP link = NULL STEP-3 If FRONT = NULL FRONT = REAR = TEMP Else REAR link = TEMP REAR = TEMP [ end of if] STEP-4 EXIT INITIALLY FRONT=NULL REAR=NULL
- 13. Algorithm to delete an element from queue STEP-1 If FRONT = NULL write underflow go to step 3. [end of if] STEP-2 set TEMP = FRONT FRONT = FRONT link if FRONT = NULL REAR = NULL STEP-3 EXIT
- 14. Types of Queues 1. Deque 2. Circular Queue 3. Priority Queue
- 15. DEQUES 1.Deque stands for double ended queue. 2.Elements can be inserted or deleted at either end. 3. Also known as head-tail linked list. 34 12 53 61 9 insertion deletion deletion insertion front rear
- 16. Types Of Deque 1.Input restricted deque: 34 12 53 61 9 deletion deletion insertion front rear 2. Output restricted deque: 34 12 53 61 9 insertion deletion insertion front rear
- 17. CIRCULAR QUEUES • Circular queue are used to remove the drawback of simple queue. • Both the front and the rear pointers wrap around to the beginning of the array. •It is also called as “Ring buffer”.
- 18. Algorithm to insert an element in queue STEP-1 If FRONT = (REAR+1)%MAX write OVERFLOW go to step 4 [end of if] STEP-2 If FRONT = -1 REAR = FRONT = 0 Else REAR = (REAR +1)%MAX [ end of if ] STEP-3 CQ[REAR] = NUM STEP-4 EXIT INITIALLY FRONT= -1 REAR= 0
- 19. Algorithm to delete an element from queue STEP-1 If FRONT = -1 write UNDERFLOW go to step 3 [ end of if ] STEP-2 If FRONT = REAR FRONT = REAR= -1 Else FRONT = (FRONT +1)%MAX STEP-3 EXIT
- 20. PRIORITY QUEUE 1.It is collection of elements where elements are stored according to the their priority levels. 2.Inserting and removing of elements from queue is decided by the priority of the elements. 3. An element of the higher priority is processed first. 4.Two element of same priority are processed on first-come-first-served basis.
- 21. Example: Suppose you have a few assignment from different subjects. Which assignment will you want to do first? subjects Due date priority DSGT 15 OCT 4 DLD 6 OCT 2 CYB 4 OCT 1 DS 8 OCT 3
- 22. APPLICATIONS Real world applications Cashier line in any store. Waiting on hold for tech support. people on an escalator. Checkout at any book store.
- 23. Applications related to computer science: 1.When data is transferred asynchronously between two processes. eg. IO Buffers. 2.When a resource is shared among multiple consumers. Examples include CPU scheduling, Disk Scheduling. 3.In recognizing palindrome. 4.In shared resources management. 5.Keyboard buffer. 6.Round robin scheduling. 7.Job scheduling. 8.Simulation