The document discusses abstract data types related to stacks and queues, highlighting their structures and operations. A stack follows a last in, first out (LIFO) approach, while a circular queue functions on a first in, first out (FIFO) principle and efficiently utilizes memory by forming a continuous loop. Additionally, it mentions priority queues which allow for the servicing of elements based on their priority level.

1. Unit 2
Stack and queues

2. STACK ADT
• A stack is an Abstract Data Type (ADT), that is
popularly used in most programming
languages. It is named stack because it has the
similar operations as the real-world stacks.
• The stack follows the LIFO (Last in - First out)
structure where the last element inserted
would be the first element deleted.

4. STACK OPERATION

5. IMPLEMENTATION OF STACK

10. APPLICATIONS OF STACK

11. EVALUATING ARITHMETIC EXPRESSION

15. QUEUE

16. IMPLEMENTATION

19. Circular Queue
• A Circular Queue is an extended version of a
normal queue where the last element of the
queue is connected to the first element of the
queue forming a circle.
• The operations are performed based on FIFO
(First In First Out) principle. It is also
called ‘Ring Buffer’.

20. • In a normal Queue, we can insert elements until
queue becomes full. But once queue becomes
full, we can not insert the next element even if
there is a space in front of queue.
• In Circular Queue, the insertion of a new
element is performed at the very first location
of the queue if the last location of the queue is
full, in which the first element comes just after
the last element.

24. • Toper form the insertion of an element to the
queue, the position of the element is
calculated by the relation as
• Rear = (Rear + 1) % Maxsize.
then set
• Queue [Rear] = value.

27. • Step 1: IF FRONT = -1
Write " UNDERFLOW "

28. Applications of Circular Queue:
• Memory Management: The unused memory
locations in the case of ordinary queues can be
utilized in circular queues.
• Traffic system: In computer controlled traffic system,
circular queues are used to switch on the traffic
lights one by one repeatedly as per the time set.
• CPU Scheduling: Operating systems often maintain a
queue of processes that are ready to execute or that
are waiting for a particular event to occur.

29. PRIORITY QUEUES
• priority queue, an element with high priority is
served before an element with low priority.
• If two elements have the same priority, they
are served according to their order in the
queue.
• Two types of priority queue
• 1. Max Priority Queue
• 2. Min Priority Queue