Coding Corner: Data Structures - Cpp Program to implement queue operations using an array

Queue is a data structure , similar to Stack , but here in queue we have openings at both the ends , one for insertion and other for deletion.

Some of the common operations of queue are :

Adding an item to queue(enqueue)
Removing an item from a queue(dequeue)
Overflow Condition(Queue full)
Underflow Condition(Queue empty)
Getting the front element(peek)

Overflow situation occur when the queue is full and then we are trying to insert/add another item to the queue .

Underflow situation occur when the queue is empty and the we are trying to remove/delete an item from the queue.

The principle of queue is First In First Out (FIFO).

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PROGRAM :

#include <iostream>

using namespace std;

int main()
{
    int rear = -1,front = -1,item,MAX ,choice ,i;
    cout << "Enter Size of Queue : \t ";
    cin >> MAX;
    int QueueArray[MAX];
    while (1)
    {
        cout << "\nQueue Operations  :";
        cout << "\n1. Insert/Add";
        cout << "\n2. Remove/Delete";
        cout << "\n3. Peek/Front item";
        cout << "\n4. Display Queue";
        cout << "\n5. Exit";
        cout << "\nEnter your choice :\t";
        cin >> choice;
        switch (choice)
        {
        case 1:
            if (rear == MAX - 1)
            {
                cout << "Queue Overflow \n";
            }
            else
            {
                if (front == -1)
                {
                    front = 0;
                }
                cout << "Inset the element in queue : \t";
                cin >> item;
                rear = rear + 1;
                QueueArray[rear] = item;
            }

            break;
        case 2:

            if (front == -1 || front > rear)
            {
                cout << "Queue Underflow \n";
                break;
            }
            else
            {
                cout << "Element deleted from queue is " <<  QueueArray[front] << "\n" ;
                front = front + 1;
            }
            break;
        case 3:
            if (front == -1 || front > rear)
            {
                cout << "Queue Underflow \n";
                break;
            }
            else
            {
                cout << "The front element is :" << QueueArray[front] << "\t" ;
            }
            break;
        case 4:
            if (front == -1 || front > rear)
            {
                cout << "Queue Underflow \n";
                break;
            }
            else
            {
                cout << "The current elements in queue are :";
                for (i = front; i <= rear; i++)
                {
                    cout << QueueArray[i];
                }
            }
            break;
        case 5:
            return 0;
            break;
        default:
            cout << "Wrong Entry \n ";
            break;
        }

    }
    return 0;
}

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