A queue performs the following commands in pseudo-code):
Enqueue 4, 6, 8, 3, 1
Dequeue three elements
Enqueue 3, 1, 5, 6
Dequeue two elements
What number is now at the front of the queue?
A) 3
B) 4
C) 5
D) 6

Question

Quizplus · Accepted Answer

Initially, the queue contains the following elements in order: 4, 6, 8, 3, 1. 
Dequeueing three elements will remove 4, 6, and 8 from the front of the queue, leaving 3 and 1. 
The Enqueue operation adds 3, 1, 5, and 6 to the end of the queue, resulting in the queue containing the elements in the order: 3, 1, 5, 6. 
Finally, dequeuing two more elements will remove 3 and 1, leaving 5 and 6 in the queue. Therefore, the number at the front of the queue is 5. As it is not given to clear the full queue so option C) 5 is incorrect. Option B) 4 is incorrect as dequeuing has removed it. Hence only option A) 3 is correct.

A Queue Performs the Following Commands in Pseudo-Code)