Queue.cpp

#include "Queue.h"
#include <iostream>
using namespace std;

//circular queue using array

QueueArray::QueueArray(int size) {
    capacity = size;
    arr = new int[capacity];
    front = -1;
    rear = -1;
    count = 0;
}

QueueArray::~QueueArray() {
    delete[] arr;
    cout << "QueueArray destroyed." << endl;
}

bool QueueArray::isEmpty() {
    if (front == -1 && rear == -1) return true;
    else  return false;
}

bool QueueArray::isFull() {
    if ((rear + 1) % capacity == front) return true;//front=0, rear=2 ->(2 + 1) % 3 = 0 == front >>> FULL
    else return false;
}

void QueueArray::enqueue(int data) {
    if (isFull()) {
        cout << "Queue is Full! Cannot add " << data << endl;
        return;
    }
    else if (isEmpty()) {
        rear = front = 0;//means exactly 1 item
        arr[rear] = data;
        count++; // first item added
        cout << data << " enqueued to queue" << endl;
    }
    else {
        rear = (rear + 1) % capacity;   // next step,wraps back to start 
        arr[rear] = data;
        count++;
        cout << data << " enqueued to queue" << endl;
    }
}

int QueueArray::dequeue() {
    if (isEmpty()) {
        cout << "Queue is empty" << endl;
        return -1; //nothing valid was returned, an error occurred
    }
    int val;
    if (front == rear) {//1 item only
        val = arr[front];
        front = rear = -1;//empty
        count--; // last item removed
    }
    else {
        val = arr[front];
        front = (front + 1) % capacity;//moving forward
        count--;
    }
    return val;
}

//  QUEUE lINKED lIST

QueueLinkedList::QueueLinkedList() {
    front = nullptr;
    rear = nullptr;
}

QueueLinkedList::~QueueLinkedList() {
    while (front != nullptr) {
        Node* temp = front;// save current front
        front = front->next;//move front to next node
        delete temp;// delete the saved node
    }
}

bool QueueLinkedList::isEmpty() {
    return front == nullptr;
}

void QueueLinkedList::enqueue(int data) {
    Node* newNode = new Node; //ifEmpty newNode=FirstNode
    newNode->data = data;
    newNode->next = nullptr;

    if (isEmpty()) {
        front = newNode;
        rear = newNode;
        //both points to FirstNode
    }
    else {
        rear->next = newNode;//creating new node
        rear = newNode;//moving the rear to the new node
    }
}

int QueueLinkedList::dequeue() {
    if (isEmpty()) {
        cout << "Queue is Empty!" << endl;
        return -1;
    }
    Node* temp = front;
    int val = temp->data;
    front = temp->next;//FIFO

    if (front == nullptr) {
        rear = nullptr;//isEmpty checked
    }

    delete temp;
    return val;
}