Implement Circular Queue via Array in C++

Introduction:

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Working Principle:

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Example:

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Code:

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// C or C++ program for insertion and
// deletion in Circular Queue
#include<bits/stdc++.h>
using namespace std;

class Queue
{
	// Initialize front and rear
	int rear, front;

	// Circular Queue
	int size;
	int *arr;
public:
	Queue(int s)
	{
	front = rear = -1;
	size = s;
	arr = new int[s];
	}

	void enQueue(int value);
	int deQueue();
	void displayQueue();
};


/* Function to create Circular queue */
void Queue::enQueue(int value)
{
	if ((front == 0 && rear == size-1) ||
			(rear == (front-1)%(size-1)))
	{
		printf("\nQueue is Full");
		return;
	}

	else if (front == -1) /* Insert First Element */
	{
		front = rear = 0;
		arr[rear] = value;
	}

	else if (rear == size-1 && front != 0)
	{
		rear = 0;
		arr[rear] = value;
	}

	else
	{
		rear++;
		arr[rear] = value;
	}
}

// Function to delete element from Circular Queue
int Queue::deQueue()
{
	if (front == -1)
	{
		printf("\nQueue is Empty");
		return INT_MIN;
	}

	int data = arr[front];
	arr[front] = -1;
	if (front == rear)
	{
		front = -1;
		rear = -1;
	}
	else if (front == size-1)
		front = 0;
	else
		front++;

	return data;
}

// Function displaying the elements
// of Circular Queue
void Queue::displayQueue()
{
	if (front == -1)
	{
		printf("\nQueue is Empty");
		return;
	}
	printf("\nElements in Circular Queue are: ");
	if (rear >= front)
	{
		for (int i = front; i <= rear; i++)
			printf("%d ",arr[i]);
	}
	else
	{
		for (int i = front; i < size; i++)
			printf("%d ", arr[i]);

		for (int i = 0; i <= rear; i++)
			printf("%d ", arr[i]);
	}
}

/* Driver of the program */
int main()
{
	Queue q(5);

	// Inserting elements in Circular Queue
	q.enQueue(14);
	q.enQueue(22);
	q.enQueue(13);
	q.enQueue(-6);

	// Display elements present in Circular Queue
	q.displayQueue();

	// Deleting elements from Circular Queue
	printf("\nDeleted value = %d", q.deQueue());
	printf("\nDeleted value = %d", q.deQueue());

	q.displayQueue();

	q.enQueue(9);
	q.enQueue(20);
	q.enQueue(5);

	q.displayQueue();

	q.enQueue(20);
	return 0;
}

Output:

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