Data structure stack&queue basics
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This document discusses stacks and queues, which are linear data structures. Stacks follow LIFO (last in, first out) and use push and pop operations. Queues follow FIFO (first in, first out) and use insertion at the rear and deletion at the front. Real-world examples of stacks include discs in a holder and tokens in a stack. Real-world examples of queues include lines at counters. Stacks and queues have various applications like reversing strings, expression evaluation, job scheduling, and memory/process management in operating systems.
![PUSHING ALGORITHM
1. Read ITEM
2. If TOP = N then Print “OVERFLOW”
and Stop
3. Else set TOP = TOP + 1
//Creating a space for a new element
4. Set STACK [ TOP ] = ITEM
//Inserting the new ITEM
5. Stop
1 2 3 4 5
TOP
N 5
NULL](https://image.slidesharecdn.com/datastructurestackqueue-basics-130512011336-phpapp01/85/Data-structure-stack-queue-basics-4-320.jpg)
![POPPING ALGORITHM
1. If TOP = NULL then
Print “UNDERFLOW” and return
2. Else set ITEM =STACK [ TOP ]
3. Set TOP = TOP - 1
4. Stop
1 2 3 4 5
TOP](https://image.slidesharecdn.com/datastructurestackqueue-basics-130512011336-phpapp01/85/Data-structure-stack-queue-basics-5-320.jpg)
![Algorithm for INSERTION
1. If FRONT = 1 and REAR = N or
If FRONT = REAR + 1 then
Print “OVERFLOW” ; stop
2. if FRONT = NULL then
set FRONT = 1 and REAR = 1
3. Else if REAR = N then
set REAR = 1
4. Else set REAR = REAR + 1
5. Endif
6. Set QUEUE [ REAR ] = ITEM
7. Stop](https://image.slidesharecdn.com/datastructurestackqueue-basics-130512011336-phpapp01/85/Data-structure-stack-queue-basics-9-320.jpg)
![Algorithm for DELETION
1. If FRONT = NULL then
Print “UNDERFLOW” ; stop
2. set ITEM = QUEUE [FRONT]
3. If FRONT = REAR then
set FRONT = NULL and REAR = NULL
4. Else if FRONT = N then set FRONT = 1
5. Else set FRONT = FRONT + 1
6. Stop](https://image.slidesharecdn.com/datastructurestackqueue-basics-130512011336-phpapp01/85/Data-structure-stack-queue-basics-10-320.jpg)
Data structure stack&queue basics
- 1. DATA STRUCTURE STACKS AND QUEUES Prepared by : SELVIN JOSY BAI.S
- 2. STACK It is a linear data structure in which an elements may be inserted or deleted only at one end called the top of the stack. This data structure implemented in LIFO (Last In First Out) manner LIFO means element last inserted would be the first one to be deleted. The Stack is also a dynamic data structure as it can grow or shrink.
- 3. Real life example : A stack OF DISCS IN HOLDER A stack of TOKENS IN HOLDER Two basic operations of stack PUSHING : An Insertion in a stack is called PUSHING. POPPING : A Deletion from a stack is called POPPING.
- 4. PUSHING ALGORITHM 1. Read ITEM 2. If TOP = N then Print “OVERFLOW” and Stop 3. Else set TOP = TOP + 1 //Creating a space for a new element 4. Set STACK [ TOP ] = ITEM //Inserting the new ITEM 5. Stop 1 2 3 4 5 TOP N 5 NULL
- 5. POPPING ALGORITHM 1. If TOP = NULL then Print “UNDERFLOW” and return 2. Else set ITEM =STACK [ TOP ] 3. Set TOP = TOP - 1 4. Stop 1 2 3 4 5 TOP
- 6. APPLICATIONS OF STACK TO REVERSING A STRING TO EVALUATE NOTATIONAL EXPRESSION(INFIX, PREFIX, & POSTFIX) TO CONVERT FROM ONE EXPRESSION TO ANOTHER.
- 7. QUEUE It is a linear data structure in which an element may be inserted only at one end, called the REAR end and deletions can be take place at the other end, called the FRONT end. This data structure implemented in FIFO (First In First Out) manner FIFO means element first inserted would be the first one to be deleted. The Queue is also a dynamic data structure as it can grow or shrink. However, if additions and deletions are made at both ends of a queue, then such a queue is called Double Ended Queue or simply DEQUE.
- 8. The following operations can be performed on Queues 1. Addition of an element at the REAR end of the queue 2. Deletion of an element from the FRONT end of the queue Real life example : • People waiting at a railway station counter for taking tickets
- 9. Algorithm for INSERTION 1. If FRONT = 1 and REAR = N or If FRONT = REAR + 1 then Print “OVERFLOW” ; stop 2. if FRONT = NULL then set FRONT = 1 and REAR = 1 3. Else if REAR = N then set REAR = 1 4. Else set REAR = REAR + 1 5. Endif 6. Set QUEUE [ REAR ] = ITEM 7. Stop
- 10. Algorithm for DELETION 1. If FRONT = NULL then Print “UNDERFLOW” ; stop 2. set ITEM = QUEUE [FRONT] 3. If FRONT = REAR then set FRONT = NULL and REAR = NULL 4. Else if FRONT = N then set FRONT = 1 5. Else set FRONT = FRONT + 1 6. Stop
- 11. APPLICATIONS OF QUEUE IT OCCURS IN THE JOB SCHEDULING THE COMPUTER OS USE THIS CONCEPT IN SCHEDULING THE MEMORY, PROCESSOR AND THE FILES. USED FOR SCHEDULING JOBS AND SERVICES.
- 12. EXERCISE - 1 In CD pack, the CDs are placed one over the other through a central axis. Assume that there are 25 CDs in the pack. a. Name the data structure that resembles with the CD pack. b. Considering the CD pack as an array in C++, how will you name the position of the last CD and what will be its value? c. Write an algorithm to remove a CD from the pack and name the operation performed.
- 13. EXERCISE - 2 While waiting for a ticket at the railway station ticket counter, you are following the principle as that of a data structure a. Name the data structure and the principle b. Write a C++ function to add a new element in this data structure. c. Name the situation where there is no space for adding new element
- 14. Some more Questions 1. What is overflow and underflow? 2. Explain the terms PUSH and POP? 3. What are the applications of stacks and queues? 4. Name the data structure that resembles a person placing plates in a vessel. Write an algorithm for inserting a plate.