Queue is a collection whose elements are added at one end and removed from the other end What is a Queue Conceptual View of a Queue Uses of Queues in Computing Operations on a Queue Implementation of a Queue Applications Downloadable Resources

1. IT 4043
Data Structures and Algorithms
Budditha Hettige
Department of Computer Science
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Queue
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2. 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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3. 3
Objectives
• Examine queue processing
• Define a queue abstract data type
• Demonstrate how a queue can be used
to solve problems

4. 4

5. 4
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

6. Conceptual View of a Queue
Front of queue
Rear of queue
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7. 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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8. 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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9. 9
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

11. Implementation of a Queue
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12. 12
An Array Implementation of a Queue

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An Array Implementation of a Queue
Before After

14. 14
An Array Implementation of a Queue

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An Array Implementation of a Queue

16. 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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17. 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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18. Thank you!
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