lecture6 Queue.pdfaonkjlasnknknlkasnncknckn

Data Structures and Algorithms EEE2020-01
Prof. Jongyoo Kim
6.
Queue

Queue
q Queue is Data Structure that save data in
§ LILO (Last-In, Last Out)
§ FIFO (First-In, First-Out)
q Type of Queue
§ Array Queue
• Implementation based on array
§ Linked Queue
• Implementation using memory allocation
Multimedia AI Lab. 2
head Data NULL
Data Data

Queue’s ADT
q void EnQueue(Datatype);
§ Insert first argument to Queue
q bool DeQueue(Datatype &);
§ Delete Data from Queue and return Data by Reference
§ If Deletion is successful, return true. If not, return false
q void PrintQueue();
§ Print Data in Queue

Main function
q Create Queue & Insert Data
q Delete Data
q Print Queue
Queue quque; Create queue
quque.enqueue(4); Insert a value(4) to the queue
quque.dequeue(tempdata); Get the value from the queue and delete it
quque.PrintList(); Print out all data in the queue
If the queue is empty, it returns false
If not, it returns true and tempdata stores the deleted value

Main function
Empty
Data : 1 2 3 4 5
Dequeue, Return data : 1
Data : 3 4 5

Array Queue
q Array : Pointer to Array
q Front : index of first input data
q Rear : index of last input data

Array Queue(Enqueue, Dequeue)
q Insert Data to Queue
q Delete Data from Queue

Problem in Array Queue
q Array is not full, but Rear can’t be increased
q To solve this problem, Rear moves to 0 for inserting data(Circular Queue).
Array
Front
Rear ………
Data
Data
0
1
…
MAX-2
MAX-1
4
Max-1
New Data Out of bound

Circular Queue
q When index is Last, Front and Rear move to 0
Rear moves to next, insert data to rear
Delete data from front, front moves to next

Problem in Circular Queue
q Relation of Front and Rear is same whether queue is full or empty
Both queue is full and empty
(Rear + 1) % Max == Front

Problem in Circular Queue
q Initialize Front, Rear to 0
q Solve Problem by wasting one data store space
If queue is full
(Rear + 1) % Max == Front
If queue is empty,
Front == Rear

Circular Queue(Contructor)
q Initialize Front, Rear, Create Array for list
Array
Front
Rear
0
0
Index 0

Circular Queue(Destructor)
q Free memory of Array
Array
Front
Rear
0
2
Index 0
D
a
t
a
D
a
t
a
D
a
t
a

Circular Queue(EnQueue)
q Insert Data to Queue
D
a
t
a
Rear
Front
Index 0
D
a
t
a
D
a
t
a
Rear
Front
Index 0
Enqueue

Circular Queue(DeQueue)
q Delete Data to From
D
a
t
a
Rear
Front
Index 0
Dequeue
D
a
t
a
D
a
t
a
Rear
Front
Index 0

Circular Queue (PrintQueue)
q If Rear is bigger than Front, Print Data from Front+1 to Rear
q If Front is bigger than Rear, Print Data from Front+1 to MAX-1, from 0 to rear

Circular Queue(PrintQueue)

CircularQueue.h

CircularQueue.cpp (1/2)

CircularQueue.cpp (2/2)

Linked Queue
§ Linked Queue’s structure is the same as a Linked List.
§ Linked Queue’s function’s rule is the same as a Linked List’s function.
§ We implement Linked Queue as a Linked List.
head Data NULL
Data Data

Second Move
First Move
Linked Queue(EnQueue)
q When the list is empty,
§ the head changes to the new node.
q When the list isn’t empty:
§ Find the last node.
• First, the last node points to the first node.
• Second, if there exists a next node for the last node, move to the next node.
• Repeat until the last node’s next node is NULL.
head Data
Last Node
NULL
Last Node Last Node
head NULL head
New Node
Data NULL
Data Data

Last Node
New Node
Linked Queue(EnQueue)
q After finding the last node, the last node’s next node changes to the new node.
q The rule for enqueue is the same as pushback in a linked list.
Data NULL
Data NULL

Linked Queue(DeQueue)
q The head changes to the first node’s next node.
q The rule for dequeue is the same as deleting the front in a linked list.
Delete Node
Data
head Data

Linked Queue(PrintQueue)
q Print the node’s data from front to back.
q The rule for PrintQueue is the same as PrintList in a linked list.

LinkedQueue.h LinkedQueue.cpp

LinkedList.h

LinkedList.cpp (1/2)

LinkedList.cpp (2/2)

main.cpp
Empty
Data : 1 2 3 4 5
Data : 3 4 5

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