A data structure that uses the first in, first out (FIFO) protocol is called a queue. In a queue, elements are added at one end and removed from the other end. This makes it similar to a real-life queue or line, where the first person to enter is the first one to exit.
How Does a Queue Work?
In a queue, elements are added at one end, known as the rear or enqueue operation. The element at the opposite end is removed first and is known as the front or dequeue operation.
A common analogy for understanding queues is to think of people waiting in line for a ticket. The person who arrives first gets served first, and as new people join the line, they are added to the rear of the queue.
The Enqueue Operation:
To add an element to a queue, we perform the enqueue operation. This operation adds an element to the rear of the queue. The newly added element becomes the last element in the queue.
To enqueue an element:
- Create a new node or item containing the data you want to add.
- If the queue is empty, set both front and rear pointers to point to this new node.
- If there are already elements in the queue, set rear’s next pointer to point to this new node and update rear pointer accordingly.
The Dequeue Operation:
To remove an element from a queue, we perform the dequeue operation. This operation removes an element from the front of the queue. The front pointer moves forward one position after deletion.
To dequeue an element:
- If the queue is empty, display an error message as there are no elements to remove.
- If there is only one element in the queue, set both front and rear pointers to null, signifying an empty queue.
- If there are multiple elements in the queue, update front’s next pointer to point to the next node and move front pointer accordingly.
Common Applications of Queues:
Queues find applications in various scenarios where data needs to be processed in a specific order. Some common applications of queues include:
- Process Scheduling: In operating systems, queues are used for scheduling processes based on priority or arrival time.
- Printer Spooling: Print jobs sent to a printer are stored in a queue and processed one at a time.
- Breadth-First Search (BFS): In graph algorithms like BFS, queues help explore neighboring nodes level by level.
A queue is a data structure that follows the FIFO protocol. It allows elements to be added at one end (rear) and removed from the other end (front).
Queues find applications in various fields such as process scheduling, printer spooling, and graph algorithms like BFS. Understanding queues is crucial for efficient data processing and algorithm design.