//Dequeue

/*

A doubly queue is a linear data structure which enables the user to add and remove integers from either ends, i.e. from front or rear. Define a class Dequeue with the following details: [10]

Class name: Dequeue
Data members/instance variables:
arr[ ]: array to hold up to 100 integer elements
lim: stores the limit of the dequeue
front: to point to the index of the front end
rear: to point to the index of the rear end
Member functions:
Dequeue(int t): constructor to initialize the data members lim = t; front = rear = -1
void addfront(int val): to add integer from the front if possible else display the message (“Overflow from front”) voidaddrear(intval): to add integer from the rear if possible else display the message (“Overflow from rear”)
int popfront(): returns element from front, if possible otherwise returns – 9999
int poprear(): returns element from rear, if possible otherwise returns – 9999
Specify the class Dequeue giving details of the constructor (int), void addfront(int), void addrear (int, popfront ( ) and int poprear ( ). The main function and algorithm need not be written.

*/

SOLUTION:

public class Dequeue

{

int arr[] ;

int lim,front,rear;

Dequeue(int t)

{

lim=t; front=-1; rear=-1;

arr=new int[lim];

}

void addfront(int val)

{

if(front>-1)

arr[front--]=val;

else

System.out.print("\n Overflow from front");

}

void addrear(int val)

{

if(rear<lim-1)

arr[++rear]=val;

else

System.out.print("\n Overflow from rear");

}

int popfront()

{

if(front!=rear)

return arr[++front];

else

return -9999;

}

int poprear()

{

if(front!=rear)

return arr[rear--];

else

return -9999;

}

void show()

{

if(front==-1 && rear==-1)

System.out.println("Empty");

else

{

for(int i=front+1;i<=rear;i++)

System.out.print(arr[i]+"   ");

}

}

public static void main(String arg[])

{

Dequeue ob=new Dequeue(5);

ob.addrear(10);

ob.addrear(20);

ob.addrear(30);

System.out.println();

ob.show();

System.out.println();

ob.addrear(40);

ob.addrear(50);

ob.show();

System.out.println();

System.out.println("DEleted No From Front is\t"+ob.popfront());

System.out.println();

ob.show();

System.out.println();

System.out.println("DEleted No From Rear is\t"+ob.poprear());

System.out.println();

ob. show();

    }

}