Question $22$

Let $Q$ denote a queue containing sixteen numbers and $S$ be an empty stack. Head$($Q$)$ returns the element at the head of the queue $Q$ without removing it from $Q.$ Similarly Top$($S$)$ returns the element at the top of $S$ without removing it from $S.$ Consider the algorithm given below.

while $Q$ is not Empty do

if $S$ is Empty OR Top $(S)$Head$(Q)$ then

$x$:$=$ Dequeue $(Q)$;

Push$(S,x)$;

else

$x$:$=P$@$p(S)$;

Enqueue $(Q,x)$;

end

end

The maximum possible number of iterations of the while loop in the algorithm is