Question

If the numbers 15, 10, 3, 42 are enqueued into a queue in that order, what does dequeue return?

Answer 1

A queue is open in both ends.In a queue data enters (enqueue) and data exits (dequeue).
Queue follows the LIFO (Last in first out) and FIFO (First in first out).
Therefore when the queue is:-

15 10 3 42
Here the data that is dequeued is 42.