Question

Suppose you are given an implementation of a queue of integers. The operations that can be performed on the queue are:

(i) is Empty (Q) : returns true if the queue is Empty, false otherwise.
(ii) delete (Q) : delete the elements at the front of the queue and returns its value.
(iii) insert (Q, i) : insert the integer i at the rear of the queue.

Consider the following functions:

void f (queue Q)
{
int i;
if (! is Empty (Q))
{
i = delete (Q);
f(Q);
insert (Q, i);
}
}

What operation is performed by the above function f?

• A. Empty the queue Q
• B. Leave the queue Q unchanged
• C. Delete the element at the front of the queue Q and insert it at the rear keeping the other elements in the same order
• D. Reverse the order of the elements in the queue Q

Answer 1

The correct option is D Reverse the order of the elements in the queue Q

Case - 1 : When queue is empty then no change would happen on queue.

Case - 2 : $1^{st}$ delete all elements one by one from queue then last deleted element enter at $2^{nd}$ position, etc.
So finally we get reverse order of given input queue.