This document discusses linear data structures, specifically stacks and queues. It defines a stack as a structure that follows LIFO principles where elements are added and removed from one end called the top. Queues follow FIFO principles where elements are added to the rear and removed from the front. The document outlines common stack and queue operations and provides examples of evaluating postfix expressions using a stack. It also discusses applications of stacks and queues in areas like expression evaluation, memory management, and networking.

1. UNIT- II
Linear data structure

2. Stack ADT
• Stack is a linear data structure in which the insertion and
deletion operations are performed at only one end. In a stack,
adding and removing of elements are performed at a single
position which is known as "top“
• In stack, the insertion and deletion operations are performed
based on LIFO (Last In First Out) principle or FILO(First In Last
Out).

3. Operations
• isFull()
• isEmpty()
• Push(x)
• Pop()
• Peek()
• Size()
• https://towardsdatascience.com/stack-
and-array-implementation-with-python-
and-nodejs-b8b260229e3a

5. Applications of stack
• used for expression evaluation.
• used to check parenthesis matching in an
expression.
• used for Conversion from one form of
expression to another.
• used for Memory Management.
• used in backtracking problems.
• https://www.youtube.com/watch?v=d_XvFOkQz
5k

6. Evaluating arithmetic
expressions
• Polish notation(Prefix) +AB
• Reverse polish notation(Postfix ) AB+
• Infix notation A+B
•A+B/*C-
•(A+B)/(C-D)
• +AB-C
•http://www.btechsmartclass.com/da
ta_structures/infix-to-postfix.html

7. Conversion of infix to postfix
notation

8. Conversion of infix to postfix
• Place parentheses around every group of operators in the
correct order of evaluation. There should be one set of
parentheses for every operator in the infix expression
• ((A * B) + (C / D))
• For each set of parentheses, move the operator from the
middle to the end preceding the corresponding closing
parenthesis.
• ((A B *) (C D /) +)
• Remove all of the parentheses, resulting in the equivalent
postfix expression.
• A B * C D / +

9. Evaluating arithmetic
expressions
Input Stack
2 3 4 * + empty Push 2
3 4 * + 2 Push 3
4 * + 3 2 Push 4
* + 4 3 2 Pop 4 and 3, and
perform 4*3 = 12.
Push 12 into the
stack.
+ 12 2 Pop 12 and 2 from
the stack, and
perform 12+2 = 14.
Push 14 into the
stack.
1) Postfix expression: 2 3 4 * +

10. Input Stack
3 4 * 2 5 * + empty Push 3
4 * 2 5 * + 3 Push 4
*2 5 * + 4 3 Pop 3 and 4 from the stack
and perform 3*4 = 12. Push
12 into the stack.
2 5 * + 12 Push 2
5 * + 2 12 Push 5
*+ 5 2 12 Pop 5 and 2 from the stack
and perform 5*2 = 10. Push
10 into the stack.
+ 10 12 Pop 10 and 12 from the
stack and perform 10+12 =
22. Push 22 into the stack.
2 )Postfix expression: 3 4 * 2 5 * +

11. Queue ADT
• Queue data structure is a collection of similar data items
in which insertion and deletion operations are performed
based on FIFO principle

12. Operations
1.enQueue(value) - (To insert an element into the queue)
2.deQueue() - (To delete an element from the queue)
3.display() - (To display the elements of the queue)
4.Queue() – creates a new empty queue
5.isEmpty()-returns a boolean value
6.Length()-returns the number of items currently in the
queue
https://www.geeksforgeeks.org/array-implementation-of-queue-
simple/

13. Circular queue
• A circular queue is a linear data structure in which the
operations are performed based on FIFO (First In First Out)
principle and the last position is connected back to the first
position to make a circle.

14. Priority queue
• Every item has a priority associated with it.
• An element with high priority is dequeued before an element
with low priority.
• If two elements have the same priority, they are served
according to their order in the queue.
Types:
1)Bounded priority queue - small limited range of p priorities
over the interval of integers [0 . . . P]
2)Unbounded priority queue - no limit on the range of integer
values

15. Doubly Ended queue(Deque)
• It allows insertion and removal of elements from
both the ends, i.e , front and back.

16. Applications of Queue
• In operating systems like Semaphores,FCFS, Buffer for
devices
• CPU task scheduling
• In networks like mail queues, queues in routers/switches
Real time application
• call center phone system to hold the calls