Here are the Basic Concept of Queue:
The Queue is a linear data structure or an abstract data type that follow the FIFO – “first in, first out” method to process the data.
• The data which is inserted first will be accessed first.
Note: Queue has two ends REAR and FRONT. The REAR end is always used to insert the data i.e., enqueue, and the FRONT end is used to remove the data inserted i.e. dequeue.
Enqueue:
The operation of adding an element to the rear (end) of the queue is called enqueue.
• New elements are added to the rear of the queue, increasing its size.
Case 1: If the queue is implemented using an array, enqueue typically involves adding an element to the end of the array.
Case 2: If it’s implemented using a linked list, a new node containing the element is appended to the end of the list.
Dequeue:
The operation of removing an element from the front of the queue is called dequeue.
• This operation removes and returns the element that was added earliest to the queue.
Case 1: If the queue is implemented using an array, dequeue typically involves removing the first element of the array and shifting the remaining elements.
Case 2: If it’s implemented using a linked list, the node at the front of the list is removed, and its value is returned.
Front:
The front (or head) of the queue refers to the element at the beginning of the queue, which will be dequeued next.
- This is the element that was added earliest to the queue.
Rear:
The rear (or tail) of the queue refers to the element at the end of the queue, where new elements are enqueued.
- This is the element that was added most recently to the queue.
Basic features of Queue
- Like stack, queue is also an ordered list of elements of similar data types.
- Queue is a FIFO ( First in First Out ) structure.
- Once a new element is inserted into the Queue, all the elements inserted before the new
element in the queue must be removed, to remove the new element. - peek( ) function is used to return the value of first element without dequeuing it.
Advantages of Queue:
‣ FIFO Ordering:
The primary advantage of queues is their adherence to the FIFO principle, which makes them suitable for applications where the order of processing matters, such as task scheduling, printing jobs, etc.
‣ Simple Implementation:
Queues are relatively simple to implement and understand. They typically have straightforward operations like enqueue (adding an element to the end) and dequeue (removing an element from the front).
‣ Efficient Insertion and Deletion:
Insertion and deletion operations in queues are typically very efficient. Enqueuing and dequeuing an item from the ends of the queue usually have constant time complexity O(1), assuming the underlying data structure is properly implemented.
‣ Resource Sharing:
Queues are often used for managing resources shared among multiple consumers. For example, in multithreading, queues can facilitate communication between threads, ensuring safe access to shared resources.
‣ Buffering:
Queues can act as buffers in systems where data production rates are not consistent with consumption rates. They help in smoothening out the flow of data, preventing bottlenecks, and overflows.
Disadvantages of Queue:
‣ Limited Access:
Unlike arrays or linked lists, queues typically provide limited access to elements. You can only access the front and rear elements, which can be restrictive in some scenarios.
‣ Dynamic Memory Allocation Overhead:
In dynamic queue implementations, where memory allocation is dynamic, there might be overhead associated with memory management. This overhead can impact performance, especially in real-time or resource-constrained systems.
‣ Not Suitable for Random Access:
Queues are not suitable for situations where random access to elements is required. Accessing elements in the middle of the queue or arbitrary locations is inefficient and often requires dequeuing multiple elements.
‣ Potential for Overflow or Underflow:
Depending on the implementation, queues may suffer from overflow (when trying to enqueue into a full queue) or underflow (when trying to dequeue from an empty queue). Proper error handling mechanisms need to be in place to handle such situations.
‣ Performance Degradation with Large Queues:
While enqueue and dequeue operations are typically efficient, the performance may degrade with a large number of elements, especially in implementations based on arrays where resizing might be required.
