Queue ppt

QUEUE
• Queue is the linear data structure type which is
used to organize the data.
• It is used for temporary storage of data values.
• A new element is added at one end called rear
end
• The existing element deleted from the other end
is called front end.
• First-in-First-out property.
2

Type of queue
Simple
Queue
Circular
Queue
Priority
Queue
Dequeue
(Double
ended
Queue)
3

Simple Queue
• Simple queue defines the simple operation of
queue in which insertion occurs at the rear of
the list and deletion occurs at the front of the
list.
4

Circular Queue
• In a circular queue, all nodes are treated as
circular. Last node is connected back to the
first node.
• Circular queue is also called as Ring Buffer.
• It is an abstract data type.
• Circular queue contains a collection of data
which allows insertion of data at the end of the
queue and deletion of data at the beginning of
the queue
5

Priority Queue
• Priority queue contains
data items which have
some preset priority.
While removing an
element from a priority
queue, the data item with
the highest priority is
removed first.
• In a priority queue,
insertion is performed in
the order of arrival and
deletion is performed
based on the priority.
7

Dequeue
(Double ended Queue)
• In Double Ended Queue, insert and delete
operation can be occur at both ends that is front
and rear of the queue
8

LINEAR
QUEUE
• A linear data structure that
stores data as a sequence of
element similar to a real
world queue.
• Possible to enter new items
from the rear end and
remove the items from the
front.
• Requires more memory.
• Less efficient.
CIRCULAR
QUEUE
• A linear data structure in
which the last item connects
back to the first item
forming a circle.
• Possible to enter and
remove elements from any
position.
• Requires less memory.
• More efficient.
9

Operations on Queue
• Enqueue() − add (store) an item to the queue.
• Dequeue() − remove (access) an item from the
queue.
• peek() − Gets the element at the front of the
queue without removing it.
• isfull() − Checks if the queue is full.
• isempty() − Checks if the queue is empty
10

Enqueue Operation
• Step 1 − Check if the queue
is full.
• Step 2 − If the queue is full,
produce overflow error and
exit.
• Step 3 − If the queue is not
full, increment rear pointer
to point the next empty
space.
• Step 4 − Add data element
to the queue location, where
the rear is pointing.
• Step 5 − return success.
11

Algorithm Of Enqueue
procedure enqueue(data)
if queue is full
return overflow
12
rear ← rear + 1
queue[rear] ← data
return true
end procedure
int enqueue (int data)
if(isfull())
return 0;
rear = rear + 1;
queue[rear] = data;
return 1;
end procedure
Example of
Enqueue
12

Dequeue Operation
• Step 1 − Check if the queue
is empty.
• Step 2 − If the queue is
empty, produce underflow
error and exit.
• Step 3 − If the queue is not
empty, access the data
where front is pointing.
• Step 4 −
Increment front pointer to
point to the next available
data element.
• Step 5 − Return success.
13

Algorithm for
dequeue operation
procedure dequeue
if queue is empty
return underflow
end if
data = queue[front]
front ← front + 1
return true
end procedure
int dequeue()
{
if(isempty())
return 0;
int data = queue[front]; front =
front + 1;
return data;
}
Example of
Dequeue Operation
14

Application of Queue
• Queue is useful in CPU scheduling, Disk
Scheduling.
• When data is transferred asynchronously
between two processes. Queue is used for
synchronization. Examples : IO Buffers, pipes,
file IO, etc.
• In real life, Call Center phone systems will use
Queues, to hold people calling them in an
order, until a service representative is free.
15

Queue ppt

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