Queue

Creating a queue:

Queue<return_type> queue;

will create a queue that stores elements of type <return_type>. The queue follows the First In, First Out (FIFO) principle, meaning the first element added is the first one to be removed.

Functions:

Function	Description	O notation
enqueue(x)	Adds the element x of type <return_type> to the queue at the end.	O(1)
dequeue()	Removes the firstly added element to the queue (if any) and returns it.	O(1)
enqueueFront(x)	Adds the element x of type <return_type> to the queue at the beginning.	O(1)
dequeueBack()	Removes the lastly added element to the queue (if any) and returns it.	O(1)
empty()	Check whether the queue is empty, returns a boolean.	O(1)
getFront()	Returns the element that's first in queue (if any).	O(1)
getBack()	Returns the element that's last in queue (if any).	O(1)

Example use case:

Queue<int> queue;
queue.enqueue(1);
queue.enqueue(2);
queue.enqueue(3);
std::cout << "Dequeued: " << queue.dequeue() << std::endl; // Dequeued: 1
queue.enqueueFront(0);
std::cout << "Dequeued from back: " << queue.dequeueBack() << std::endl; // Dequeued from back: 3
std::cout << "Queue empty? " << (queue.empty() ? "Yes" : "No") << std::endl; // Queue empty? No