A queue is a data structure that follows the First-In-First-Out (FIFO) principle, where the first element added to the queue is the first one to be removed. This makes it an ideal data structure for situations where elements need to be processed in the order they were received. In this article, we will discuss the implementation of queues using linked lists in C++.
A linked list is a data structure that consists of a series of nodes, where each node contains a value and a pointer to the next node in the list. Linked lists are dynamic in nature, which means that they can grow or shrink as needed. This makes them an ideal choice for implementing queues as elements can be added and removed as needed.
The first step in implementing a queue using linked lists is to create a node structure. The node structure should contain a value and a pointer to the next node in the list. The following is an example of a node structure in C++:
struct Node { int value; Node* next; };
Once the node structure is defined, we can create a queue class that contains a pointer to the front and back of the list. The front pointer will always point to the first element in the queue and the back pointer will always point to the last element in the queue. The following is an example of a queue class in C++:
class Queue { private: Node* front; Node* back; public: Queue() { front = nullptr back = nullptr; } // Other functions };
The next step is to implement the enqueue function, which will be used to add elements to the queue. The enqueue function should create a new node with the given value and add it to the back of the queue. If the queue is empty, the front and back pointers should point to the new node. If the queue is not empty, the back pointer should be updated to point to the new node. The following is an example of an enqueue function in C++:
void Queue::enqueue(int value) { Node* newNode = new Node; newNode->value = value; newNode->next = nullptr; if (back == nullptr) { front = newNode; back = newNode; }else { back->next = newNode; back = newNode; }
}
The next step is to implement the dequeue function, which will be used to remove elements from the queue. The dequeue function should remove the first element in the queue and return its value. If the queue is empty, the function should return an error. The following is an example of a dequeue function in C++:
int Queue::dequeue() { if (front == nullptr) { throw "Error: Queue is empty"; } Node* temp = front; front = front->next;
int value = temp->value; delete temp; if (front == nullptr) { back = nullptr; } return value; }
Finally, it is important to implement the peek function, which will be used to return the value of the first element in the queue without removing it. The peek function should return the value of the
