Dqueue

Dqueue is a data structure that represents a double-ended queue. It is a linear collection of elements that allows for efficient insertion and deletion of elements from both the front and the back. Unlike a standard queue where elements are added at one end and removed from the other (FIFO - First-In, First-Out), a dqueue provides flexibility by enabling operations at either end.

The primary operations on a dqueue include adding an element to the front, adding an element to the back, removing an element from the front, and removing an element from the back. Accessing the element at the front or back without removing it is also a common operation. These operations are typically performed in constant time, denoted as O(1), making dqueues very efficient for specific use cases.

Dqueues can be implemented using various underlying structures, such as arrays or linked lists. An array-based implementation might use a circular buffer to manage the two ends effectively. A linked list implementation would involve managing pointers at both the head and the tail of the list.

The applications of dqueues are diverse. They are useful in algorithms where elements might need to be processed in a non-linear fashion, such as in certain breadth-first search implementations or for managing a history of actions where undoing or redoing operations from either end is desired. They are also employed in sliding window problems and for maintaining a deque of recently accessed items.