Question

A double ended queue is a linear data structure which enables the user to add and remove integers from either ends i.e., from front or rear.

The details for the class deQueue are given below:

Class name	deQueue
Data members/instance variables:
Qrr[]	array to hold integer elements
lim	maximum capacity of the dequeue
front	to point the index of the front end
rear	to point the index of the rear end
Methods/Member functions:
deQueue(int 1)	constructor to initialise lim = 1, front = 0 and rear =0
void addFront(int v)	to add integers in the dequeue at the front end if possible, otherwise display the message “OVERFLOW FROM FRONT”
void addRear(int v)	to add integers in the dequeue at the rear end if possible, otherwise, display the message “OVERFLOW FROM REAR”
int popFront()	removes and returns the integers from the front end of the dequeue if any, else returns — 999
int popRear ( )	removes and returns the integers from the rear end of the dequeue if any, else returns — 999
void show( )	displays the elements of the dequeue

Specify the class deQueue giving details of the function void addFront(int) and int popFront(). Assume that the other functions have been defined. The main() function and algorithm need NOT be written.

Answer 1

class deQueue
{
int Qarr[];
int lim;
int front;
int rear;
public deQueue(int l)
{
   lim=l;
   front=-1;
   rear=-1;
   Qarr[]=new Qarr[l];
}
public void addFront(int v)
{
   if((front=0 && rear=lim-1) || (front=rear+1))
      System.out.println(“Overflow from front”);
  else if((front=-1) && (rear=-1))
  { front=rear=0;
     Qarr{front]=v;
 }
 else if (front=0)
 {  front=lim-1;
    Qarr{front]=v;
       }
  else
  {
     front=front-1;
    Qarr[front]=v;
    }
}
    public void popFront()
   {
        if((front=-1) &&c (rear=-1))
           {
              System.out.println(“Deque is empty”);
           }
     else if(front=rear)
     {
        System.out.println(“The deleted element is :”,
        Qarr[front]);
        front=-1;
        rear=-1;
     }
     else if(front=(size-1))
     {
        System.out.println(“The deleted element is :",
        Qarr[front]);
        front=0;
    }
    else
    {
       System.out.println(“The deleted element is :",
       Qarr[front]);
       front=front+1;
     }
  }
}