This document provides an outline and overview of the queue data structure. It defines a queue as a first-in, first-out (FIFO) structure where new items are added to the rear of the queue and items are removed from the front. The key queue operations of enqueue and dequeue are described. Code examples are provided for implementing a queue using a linked list structure with classes for the queue, its nodes, and methods for common queue operations like enqueue, dequeue, peek, clear, print, and search. Different types of queues like linear, circular, and double-ended queues are also mentioned.

1. DATA STRUCTURE
Chapter 7: Queue
Prepared & Presented by
Mr. Mahmoud R. Alfarra
2011-2012
College of Science & Technology
Dep. Of Computer Science & IT
BCs of Information Technology
http://mfarra.cst.ps

2. Out Line
 What is Queue data structure?
 EnQueue operation
 DeQueue operation
 Clear the Queue
 Print all data of Queue
 Search about data
 Queue Class
 Types of Queue
2

3. What is Queue data
structure?
 Queues are used to prioritize operating system
processes and to simulate events in the real
world, such as teller lines at banks and the
operation of elevators in buildings.
 A queue is a data structure where data enters at
the rear of a list and is removed from the front of
the list.
 Queues are an example of a first-in, first-out
(FIFO) data structure.
3
Mohame
d
Ghadeer
Ali
Ahmed
Hussam
Rear Front

4. Queue Operations
 The two primary operations involving queues
are adding a new item to the queue and
removing an item from the queue.
 The operation for adding a new item is called
Enqueue, and the operation for removing an
item from a queue is called Dequeue.
 The other primary operation (The Peek
method) to perform on a queue is viewing the
beginning
 item.
4

5. What is Queue data
structure?
5

6. Element of Queue
6
‫البيانات‬ ‫تراكيب‬ ‫مساق‬
‫إعداد‬ ‫العلمية‬ ‫المادة‬
/
‫أ‬
.
‫ا‬ َّ‫الفــر‬ ‫رفيق‬ ‫محمود‬
 Exactly as linked list and stack …

7. 1- Element of Queue
(customer)
7
‫البيانات‬ ‫تراكيب‬ ‫مساق‬
‫إعداد‬ ‫العلمية‬ ‫المادة‬
/
‫أ‬
.
‫ا‬ َّ‫الفــر‬ ‫رفيق‬ ‫محمود‬
1. class Customer {
2. public int parts;
3. public int amount;
4. public String name;
5. public Customer next;
6. public Customer() {
7. parts = 0;
8. amount = 0;
9. name = "no name"; }
10. public Customer(int parts, int amount, String name) {
11. this.parts = parts;
12. this.amount = amount;
13. this.name = name; } }

8. 2- Class Queue of customer
8
‫البيانات‬ ‫تراكيب‬ ‫مساق‬
‫إعداد‬ ‫العلمية‬ ‫المادة‬
/
‫أ‬
.
‫ا‬ َّ‫الفــر‬ ‫رفيق‬ ‫محمود‬
1. class QueueOfCustomer {
2. public Customer Front;
3. public Customer Rear;
4. public int length;
5. public QueueOfCustomer()
6. {
7. Front = null;
8. Rear = null;
9. length = 0;
10. }
11.}

9. EnQueue Operation
9
Mohame
d
Ghadeer
Ali
Rear Front
Ahmed
New item
1
2
X

10. EnQueue Operation
10
1. public void InQueue(Customer addCus)
2. {
3. Customer newc = addCus;
4. if (Front == null)
5. {
6. Front = newc;
7. Rear = newc;
8. newc.next = null;
9. }
10. else
11. {
12. newc.next = Rear;
13. Rear = newc;
14. }
15. length++;
16. Console.WriteLine("The new Object is added: "+length);
17. }

11. DeQueue operation
11
Mohame
d
Ghadeer
Ali
Rear Front
Ahmad
current

12. DeQueue operation
12
1. public void DeQueue() {
2. if (Front == null)
3. Console.WriteLine("The Queue is Empty!!");
4. else
5. {
6. Customer current;
7. Customer pre_current = Rear;
8. for (current = Rear; current.next != null; current =
current.next)
9. pre_current = current;
10. Front = pre_current;
11. length--;} }

13. Peek Operation
13
Front.name
front.salary
…
Front

14. Peek Operation
14
‫البيانات‬ ‫تراكيب‬ ‫مساق‬
‫إعداد‬ ‫العلمية‬ ‫المادة‬
/
‫أ‬
.
‫ا‬ َّ‫الفــر‬ ‫رفيق‬ ‫محمود‬
1. public void Peek()
2. {
3. if (Front == null)
4. Console.WriteLine("The Queue is empty");
5. else
6. Console.WriteLine("The Data of the first is:n "+
7. Front.name +"n "+Front.amount+"n "+Front.parts);
8. }

15. Clear the Queue
15
1. public void Clear()
2. {
3. if (Rear == null)
4. Console.WriteLine("The Queue is Empty!!");
5. else
6. Rear = null;
7. Length = 0;
8. }

16. Print all data of Queue
16
Mohame
d
Ghadeer
Ali
Rear Front
Ahmed
current current current current

17. Print all data of Queue
17
‫البيانات‬ ‫تراكيب‬ ‫مساق‬
‫إعداد‬ ‫العلمية‬ ‫المادة‬
/
‫أ‬
.
‫ا‬ َّ‫الفــر‬ ‫رفيق‬ ‫محمود‬
1. public void PrintAll()
2. {
3. Customer current;
4. for (current = Rear; current != null; current = current.next)
5. {
6. Console.WriteLine(" ========================== ");
7. Console.WriteLine("The Data of the element is:n " +
8. current.name + "n " + current.amount + "n " + current.parts);
9. Console.WriteLine(" ========================== ");
10. }
11. }

18. Search about data
18
Mohame
d
Ghadeer
Ali
Rear Front
Ahmed
current current current current

19. Search about data
19
‫البيانات‬ ‫تراكيب‬ ‫مساق‬
‫إعداد‬ ‫العلمية‬ ‫المادة‬
/
‫أ‬
.
‫ا‬ َّ‫الفــر‬ ‫رفيق‬ ‫محمود‬
1. public void SearchByAmount(int amount)
2. {
3. Customer current = Rear;
4. bool flag = false;
5. while (current != null)
6. {
7. if (current.amount == amount)
8. {
9. flag = true;
10. break;
11. }
12. current = current.next;
13. }
14. if (flag == true)
15. Console.WriteLine("The element is exist!! ");
16. else
17. Console.WriteLine("The element does not exist!! ");
18. }

20. Queue Class
 Class of Queue available in collection space of
.Net.
20
Practice : develop a full
application using class of Queue

21. Types of Queue
 Linear queue
 Circular queue
 Double ended queue

22. Thank You …
22
Remember that: question is the key of knowledge

23. Ahl Eljanna 

َ
‫ه‬َ‫ن‬َ
‫و‬ ٍ
‫َّات‬‫ن‬َ
‫ج‬ ِ
‫ِف‬ َ
‫ني‬ِ
‫َّق‬‫ت‬ُ
‫ْم‬‫ل‬‫ا‬ َّ
‫ن‬ِ‫إ‬
ٍ
‫ر‬
)::(
ِ
‫ع‬ ٍ
‫ق‬ْ
‫د‬ِ
‫ص‬ ِ
‫د‬َ
‫ع‬ْ
‫ق‬َ
‫م‬ ِ
‫ِف‬
َ
‫د‬ْ‫ن‬
ٍ
‫ر‬ِ
‫د‬َ‫ت‬ْ
‫ق‬ُ
‫م‬ ٍ
‫يك‬ِ‫ل‬َ
‫م‬
)::(
23