Introduction and implementation of queues (queue)

Queues are another simple and common data structure. Queues are also ordered collections of elements. The most important feature of the queue is first in, first-out (FIFO, first-in), which is an interesting contrast to stacks (stack). Queues are common in life, queuing for tickets, waiting for a bus ... First-come people get the service first and leave the queue, and later people join the queue at the end. Queues are a fairly distributed way of allocating limited resources, allowing people in queues to get services at similar waiting times.

The queue supports two operations, the team head element leaves the queue (dequeue), and the new element joins the team tail (enqueue).