finalinternalppt

8/7/2019 finalinternalppt

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STACKS AND QUEUES



STACK OVERVIEW

Stack A T Basic operations of stack

Pushing, popping etc.

Implementations of stacks using ± array

± linked list



Stac ADTA stac is a li ear ata structure i w ic ite s are

i serte a elete at t e sa e e w ic is

w as t e t f t e stac.

Stac s are w as LIFO (Last I , First Out) lists T e

last ele e t i serte will be t e first t be retrieve



� Push:Add an element to the top of the stack

Pri ar O erati s

top

empty stack

Atop

push an element

top

push another

A

B

top

Stack full

A

B

B

C



top

A

top

pop an element

top

pop another

A

B

empty stack

Pop

Remove the element at the top of the stack

C

B

A

B

Stack Full

Pri ar O erati s



Pseu c e f r Pus erati f stac

Sub us (stac 1,t ,ele e t,size)

If t >=size t e

Dis la ³stac verfl w´

retur

E if t =t +1

stac 1[t ]=ele e t

retur

e sub



Pseu c e f r Pop operation of stac

sub pop[stac 1,top]

if top=0 t endis pla ³stac in underflow´

exit

endif top<=top-1

retur n[s(top+1)]

endsub



A pplication of stac

Conversion of ex pressions: Using stac s we can

easil convert ex pressions fr om infix to postfix, prefix to

postfix etc Evaluation of ex pressions: An ex pression written in

t e f or m of postfix or prefix can be easil evaluated

Recursion: Stac s can also be used in recursive

functions

Runtime memory management: Stacks are used in run

time memory management



Stack Implementation

Stack can be implemented in two different wa s:

1. Con

tiguo

us stack

: t e stack

is imp

lem

en

ted

as an arra .

2. Link ed stack : pointers and dynamic memor y allocation is

used to implement t e stack .



QUEUES OVERVIEW

. . Queue ADT

asic operations of queue

Enqueuing, dequeuing etc.

Implementation of queueArray

Link ed list



A queue is an or dered gr ou p of omogeneous items(elements), in w ich new elements are added at one end (the rear), and elements are removed fr om the other end

(the fr ont).A queue is lik e a line of people waiting f or a bank teller.The queue has a front and a rear. A queue is a FIFO³f irst in, f irst out´ structur e

QUEUE ADT

$ $

Fr ontRear



Queue O perations

Enqueue: New people must enter the queue at the

rear. The C++ queue class calls this a push, although

it is usually called an enqueue operation

$ $

Fr ont

Rear



Queue O perations

Dequeue :When an item is tak en fr om the queue, it

always comes fr om the fr ont. The C++ queue calls

this a pop, although it is usually called a dequeueoperation

$ $

Fr ont

Rear



sub insertrear(rear,item,queue1,queuesize )

If(rear==queuesize-1)dis play ´queue overflow´

retur n

endif

rear=rear+1queue1[rear]=item

endsub

Pseudocode f or Enqueue operation of Queue



Pseudocode f or Dequeue operation of Queue

sub deletefr ont(queue1,fr ont,rear)

If(fr ont>rear)

dis play ´queue underflow´retur n

Endif

Dis play´element deleted is queue1[(fr ont)++)

If(fr ont>rear)

fr ont=0,rear=-1

endif

Endsub



Types of queues

Or dinar y Queue

Cir cular Queue

Double Ended Queue

Priority Queue



Cir cular Queue

A cir cular Queue is used to over come

a disadvantage of an or dinar y queue

where we cannot insert elements in

queue once its full even if free slotsare available

A cir cular Queue solves the pr o blem

by using this equation

Rear=rear+1%queuesize

rather than

Rear=rear+1



A pplications of Queues

Direct applications

Waiting lists, bureaucracyAccess to shared resour ces (e.g., printer)

Multi pr ogramming

Indirect applications

Auxiliar y data structure f or algorithms

Component of other data structures



Implementation of Queue

Just as stack s can be implemented as arrays or

link ed lists, so with queues.

Dynamic queues have the same advantages

over static queues as dynamic stack s have over

static stack s



THANK YOUTHANK YOU

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