What is D-Queue?

A deque (double-ended queue) is a linear data structure that allows for the insertion and deletion of elements at both ends. It is similar to a stack, which allows for the insertion and deletion of elements at one end only, and a queue, which allows for the insertion of elements at one end and the deletion of elements at the other end.

Deques are often implemented using an underlying array or linked list data structure. They support the following operations:

insertFront: Insert an element at the front of the deque

insertBack: Insert an element at the back of the deque

removeFront: Remove the element at the front of the deque

removeBack: Remove the element at the back of the deque

peekFront: Return the element at the front of the deque without removing it

peekBack: Return the element at the back of the deque without removing it

Deques are useful in situations where it is necessary to insert or delete elements at both ends of a data structure. They are often used as a building block for other data structures, such as stacks, queues, and priority queues.

Deques are also known as double-ended queues, double-ended heaps, or ring buffers.

Deques have a fixed size, which is determined when the deque is created. If a deque becomes full and a new element needs to be inserted, an overflow error will occur. This can be avoided by using a dynamically resizing deque, which automatically increases its size as needed.

Deques can be implemented using an array or a linked list. Array-based deques have a fixed size and offer fast random access to elements, but they can be slower to insert and delete elements compared to linked list-based deques. Linked list-based deques are more flexible in terms of size, but they do not offer fast random access to elements.

Deques can be used to implement a variety of data structures, including stacks, queues, and priority queues. They can also be used to implement algorithms for tasks such as sorting and searching.

Some programming languages (such as Python and Java) have built-in deque data structures or classes that can be used to create deques.