Lecture 4:: simple Queue and circular Queue

Queues are data structures that follow the First In First Out (FIFO) i.e. the first element that is added to the queue is the first one to be removed.
In a queue data structure, the insertion operation is performed using a function called enqueue( based on index rear)and deletion operation is performed using a function called dequeue(based on index front).
As in stacks, a queue can also be implemented using Arrays, Linked-lists. For the sake of simplicity, we shall implement queues using one-dimensional array.
There are two types of queue: Simple And Circular queue.

Algorithm 1: enqueue
Inputs: Q: array as integer, f: front pointer, r: rear pointer, n: size of queue, x: the new element
Outputs: insert x to Q.
Begin
If ( r = n-1 ) then
Write ("Queue is over flow")
Else
r = r + 1
Q[r]=x
If ( f = -1) then
F=0
End



Example 1:: Suppose a queue with size 5 do the following ::
1- Insert the elements (25, 30, 51, 60 and 85)

25 30 51 60 85





2- Perform the dequeue for three times
60 85



Example 2::What the operation that perform on (a) to obtain (b)