package stack_and_queue;

import java.util.ArrayList;

// implement `circular queue

// Java program for insertion and

// deletion in Circular Queue

class P25{

// Declaring the class variables.

private int size, front, rear;

// Declaring array list of integer type.

private ArrayList<Integer> queue = new ArrayList<Integer>();

// Constructor

P25(int size)

{

this.size = size;

this.front = this.rear = -1;

}

// Method to insert a new element in the queue.

public void enQueue(int data)

{

// Condition if queue is full.

if((front == 0 && rear == size - 1) ||

(rear == (front - 1) % (size - 1)))

{

System.out.print("Queue is Full");

}

// condition for empty queue.

else if(front == -1)

{

front = 0;

rear = 0;

queue.add(rear, data);

}

else if(rear == size - 1 && front != 0)

{

rear = 0;

queue.set(rear, data);

}

else

{

rear = (rear + 1);

// Adding a new element if

if(front <= rear)

{

queue.add(rear, data);

}

// Else updating old value

else

{

queue.set(rear, data);

}

}

}

// Function to dequeue an element

// form th queue.

public int deQueue()

{

int temp;

// Condition for empty queue.

if(front == -1)

{

System.out.print("Queue is Empty");

// Return -1 in case of empty queue

return -1;

}

temp = queue.get(front);

// Condition for only one element

if(front == rear)

{

front = -1;

rear = -1;

}

else if(front == size - 1)

{

front = 0;

}

else

{

front = front + 1;

}

// Returns the dequeued element

return temp;

}

// Method to display the elements of queue

public void displayQueue()

{

// Condition for empty queue.

if(front == -1)

{

System.out.print("Queue is Empty");

return;

}

// If rear has not crossed the max size

// or queue rear is still greater then

// front.

System.out.print("Elements in the " +

"circular queue are: ");

if(rear >= front)

{

// Loop to print elements from

// front to rear.

for(int i = front; i <= rear; i++)

{

System.out.print(queue.get(i));

System.out.print(" ");

}

System.out.println();

}

// If rear crossed the max index and

// indexing has started in loop

else

{

// Loop for printing elements from

// front to max size or last index

for(int i = front; i < size; i++)

{

System.out.print(queue.get(i));

System.out.print(" ");

}

// Loop for printing elements from

// 0th index till rear position

for(int i = 0; i <= rear; i++)

{

System.out.print(queue.get(i));

System.out.print(" ");

}

System.out.println();

}

}

// Driver code

public static void main(String[] args)

{

// Initialising new object of

// CircularQueue class.

P25 q = new P25(5);

q.enQueue(14);

q.enQueue(22);

q.enQueue(13);

q.enQueue(-6);

q.displayQueue();

int x = q.deQueue();

// Checking for empty queue.

if(x != -1)

{

System.out.print("Deleted value = ");

System.out.println(x);

}

x = q.deQueue();

// Checking for empty queue.

if(x != -1)

{

System.out.print("Deleted value = ");

System.out.println(x);

}

q.displayQueue();

q.enQueue(9);

q.enQueue(20);

q.enQueue(5);

q.displayQueue();

q.enQueue(20);

}

}

// This code is contributed by Amit Mangal.