Data Structures and Algorithms Queue - WordPress.com · 4 Queue •Queue: a collection whose elements are added at one end (the rear or tail of the queue) and removed from the other

IT 4043

Data Structures and Algorithms

Budditha Hettige

Department of Computer Science

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Queue

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Course Outline• Introduction to DSA

• Abstract Data Types (ADT)

• List operation using arrays

• Stacks

•Queues• Recursion

• Link List

• Sorting

• Searching

• Algorithms Analysis

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Objectives

• Examine queue processing

• Define a queue abstract data type

• Demonstrate how a queue can be used

to solve problems

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Queue• Queue: a collection whose elements are

added at one end (the rear or tail of the queue) and removed from the other end (the front or head of the queue)

• A queue is a FIFO (first in, first out) data structure

• Any waiting line is a queue:

–The check-out line at a grocery store

–The cars at a stop light

–An assembly line

Conceptual View of a Queue

Front of queue

Rear of queue

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Conceptual View of a Queue

Front of queue

Adding an element

The new element is added to the rear of the queue

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Removing an element

New front element of queue

The element is removed from the front of the queue

Conceptual View of a Queue

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Uses of Queues in Computing

• Printer queue

• Keyboard input buffer

• GUI event queue (click on buttons, menu items)

• To encode messages

• For any kind of problem involving FIFO data

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Operations on a Queue

Operation Description

remove Removes an element from the front of the queue

insert Adds an element to the rear of the queue

isFull Determines whether the queue is full

isEmpty Determines whether the queue is empty

Implementation of a Queue

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An Array Implementation of a Queue

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An Array Implementation of a Queue

Before After

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An Array Implementation of a Queue

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An Array Implementation of a Queue

Summary• Queue: a collection whose elements are

added at one end and removed from the

other end

• A queue is a FIFO (first in, first out) data

structure

• Queue Implementation (Java)

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Questions

1. Specify 3 usages of Queues in Computing.

2. Identify which of the following is/are true? In

each case justify your answer.

a. Web browsers use queues to retrieve data

b. In the front fix array bases queue

implementation, remove operation is less

efficient than insert

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Thank you!

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