This document discusses the uses of stacks and queues. It describes how stacks can be used to solve problems involving parenthesis matching and rearranging railroad cars. It then defines queues as first-in first-out data structures, where the element inserted first is the first one deleted. Examples of queues include people waiting in line at the bank. The document notes that underflow occurs if an empty queue is deleted, while overflow happens if the rear of the queue exceeds its size. Insertion and deletion from queues are called enqueue and dequeue, respectively.

1. Lecture # 7Lecture # 7

2. Uses of StackUses of Stack
Discussing Two Problems:Discussing Two Problems:
Parenthesis MatchingParenthesis Matching
(Book Page No 252, sahni)(Book Page No 252, sahni)
Rearranging Railroad CarsRearranging Railroad Cars
(Book Page No 256, sahni)(Book Page No 256, sahni)

3. QueueQueue

4.  Figure showing Queue…..Figure showing Queue…..
BA EC
frontfront
rearrear
D NULLNULL

5.  In aIn a queuequeue, the element, the element deleteddeleted from the list isfrom the list is
the one whichthe one which inserted firstinserted first..
 QueueQueue is also referred asis also referred as First-in First-outFirst-in First-out i.ei.e
FIFOFIFO..
 TheThe exampleexample of queue is theof queue is the queue of peoplequeue of people
standing for submitting their bills in the bank.standing for submitting their bills in the bank.
The one who joins the queueThe one who joins the queue firstfirst also leavesalso leaves
the queuethe queue firstfirst . Similarly who joins the queue at. Similarly who joins the queue at
lastlast, leaves the queue at, leaves the queue at lastlast..

6.  If anIf an emptyempty queue is deleted, we say queuequeue is deleted, we say queue
underflowsunderflows andand
 If rear of the queue exceedsIf rear of the queue exceeds nn, the queue, the queue
overflowsoverflows..
 InsertionInsertion to queue is calledto queue is called EnqueueEnqueue andand deletiondeletion
form queue is calledform queue is called DequeueDequeue..

7.  Implementation on board - DiscussionImplementation on board - Discussion

8. Thank You……Thank You……