What is Queue Data Structure?
A Queue is defined as a linear data structure that is open at both ends and the operations are performed in First In First Out (FIFO) order.
We define a queue to be a list in which all additions to the list are made at one end, and all deletions from the list are made at the other end. The element which is first pushed into the order, the operation is first performed on that.
FIFO Principle of Queue:
- A Queue is like a line waiting to purchase tickets, where the first person in line is the first person served. (i.e. First come first serve).
- Position of the entry in a queue ready to be served, that is, the first entry that will be removed from the queue, is called the front of the queue(sometimes, head of the queue), similarly, the position of the last entry in the queue, that is, the one most recently added, is called the rear (or the tail) of the queue. See the below figure.
Basic Operations
Queue operations also include initialization of a queue, usage and permanently deleting the data from the memory.
The most fundamental operations in the queue ADT include: enqueue(), dequeue(), peek(), isFull(), isEmpty(). These are all built-in operations to carry out data manipulation and to check the status of the queue.
Queue uses two pointers − front and rear. The front pointer accesses the data from the front end (helping in enqueueing) while the rear pointer accesses data from the rear end (helping in dequeuing).
Insertion operation: enqueue()
The enqueue() is a data manipulation operation that is used to insert elements into the stack. The following algorithm describes the enqueue() operation in a simpler way.
Deletion Operation: dequeue()
The dequeue() is a data manipulation operation that is used to remove elements from the stack. The following algorithm describes the dequeue() operation in a simpler way.
The peek() Operation
The peek() is an operation which is used to retrieve the frontmost element in the queue, without deleting it. This operation is used to check the status of the queue with the help of the pointer.
The is Full() Operation
The is Full() operation verifies whether the stack is full.
The is Empty() operation
The is Empty() operation verifies whether the stack is empty. This operation is used to check the status of the stack with the help of top pointer.
