Lecture 253:- Let's Code Queue in C++

Here's the implementation of a Queue in C++ using an array:

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#include <iostream> const int MAX_SIZE = 100; class Queue { private:    int arr[MAX_SIZE];    int frontIdx;    int rearIdx; public:    Queue() {        frontIdx = -1;        rearIdx = -1;    }    bool isEmpty() {        return frontIdx == -1 && rearIdx == -1;    }    bool isFull() {        return (rearIdx + 1) % MAX_SIZE == frontIdx || (frontIdx == 0 && rearIdx == MAX_SIZE - 1);    }    void enqueue(int element) {        if (isFull()) {            std::cout << "Queue is full. Cannot enqueue." << std::endl;            return;        }        if (isEmpty()) {            frontIdx = 0;        }        rearIdx = (rearIdx + 1) % MAX_SIZE;        arr[rearIdx] = element;    }    void dequeue() {        if (isEmpty()) {            std::cout << "Queue is empty. Cannot dequeue." << std::endl;            return;        }        if (frontIdx == rearIdx) {            frontIdx = -1;            rearIdx = -1;        } else {            frontIdx = (frontIdx + 1) % MAX_SIZE;        }    }    int front() {        if (isEmpty()) {            std::cout << "Queue is empty." << std::endl;            return -1; // Assuming -1 is not a valid element in the queue.        }        return arr[frontIdx];    }    int size() {        if (isEmpty()) {            return 0;        }        return (rearIdx >= frontIdx) ? (rearIdx - frontIdx + 1) : (MAX_SIZE - frontIdx + rearIdx + 1);    } }; int main() {    Queue queue;    queue.enqueue(10);    queue.enqueue(20);    queue.enqueue(30);    std::cout << "Front element: " << queue.front() << std::endl;    queue.dequeue();    std::cout << "Front element after dequeue: " << queue.front() << std::endl;    std::cout << "Queue size: " << queue.size() << std::endl;    return 0; }

In this implementation, we use an array to store the elements of the queue. The queue has a maximum size of MAX_SIZE defined as 100. The Queue class contains private member variables frontIdx and rearIdx to keep track of the front and rear positions in the queue.

The member functions isEmpty() and isFull() check if the queue is empty or full, respectively. The enqueue() function adds an element to the rear of the queue, the dequeue() function removes the front element from the queue, and the front() function returns the front element without removing it. The size() function returns the number of elements in the queue.

In the main function, we demonstrate how to use the Queue by enqueueing and dequeueing elements and checking the front element and queue size.