How is a queue implemented in C++?

C++ queues can be implemented using two methods: arrays and linked lists.

1. Array implementation: Using an array to store the elements of the queue, and using two pointers front and rear to respectively point to the head and tail of the queue. When the queue is empty, front and rear point to the same position; when adding elements to the queue, the element is added to the position pointed to by rear, and rear is moved one position backwards; when deleting elements from the queue, front is moved one position backwards, and the element pointed to by front is returned. If the queue is full, elements cannot be added.
2. Linked list implementation: Using a linked list to store the elements of the queue, each node contains a data element and a pointer to the next node. Two pointers, front and rear, respectively point to the head and tail of the queue. When the queue is empty, both front and rear point to null; when adding elements to the queue, create a new node and connect it to the node pointed to by rear, and then move rear to the new node; when removing elements from the queue, delete the node pointed to by front and move front to the next node. A queue implemented with a linked list does not have a fixed size limit.

Whether implemented using arrays or linked lists, queue operations include enqueue, dequeue, check if the queue is empty, etc.