Question

Show what is written by following segments of code, given that element1, element2, and element3, are int variables, and queue is an object that fits the abstract description of a queue as given in Section 5.2. Assume that you can store and retrieve values of type int in queue.

a.

element1 = 1;

element2 = 0;

element3 =4

queue.enqueue(element2);

queue.enqueue(element1);

queue.enqueue(element1 + element3);

element2 = queue.dequeue()

queue.enqueue(element3 * element3);

queue.enqueue(element2);

queue.enqueue(3);

element1 = queue.dequeue();

System.out.println(element1 + “ “ + element2 + “ “ + element3);

while (!queue.isEmpty())

{

   element1 = queue.dequeue();

   System.out.println(element1);

}

b.

element1 = 4;

element3 = 0;

element2 = element1 + 1;

queue.enqueue(element2);

queue.enqueue(element2 + 1);

queue.enqueue(element1);

element2 = queue.dequeue()

element1 = element2 +1;

queue.enqueue(element1);

queue.enqueue(element3);

while (!queue.IsEmpty())

{

element1 = queue.dequeue();

System.out.println(element1);

}

System.out.println(element1 + “ “ + element2 + “ “ + element3);

Answer 1

/* java program implementing Dequeue operation */

import java.lang.reflect.Array;

class Deque<Item>
{
private int maxSize=100;
private final Item[] array;
private int front,rear;
private int numberOfItems;
public Deque()
{
array=(Item[])(new Object[maxSize]);
front=0;
rear=-1;
numberOfItems=0;
}
public boolean isEmpty()
{
return (numberOfItems==0);
}
public void addFirst(Item item)
{
if(front==0)
front=maxSize;
array[--front]=item;
numberOfItems++;
}
public void addLast(Item item)
{
if(rear==maxSize-1)
rear=-1;
array[++rear]=item;
numberOfItems++;
}
public Item removeFirst()
{
Item temp=array[front++];
if(front==maxSize)
front=0;
numberOfItems--;
return temp;
}
public Item removeLast()
{
Item temp=array[rear--];
if(rear==-1)
rear=maxSize-1;
numberOfItems--;
return temp;
}
public int getFirst()
{
return front;
}
public int getLast()
{
return rear;
}
public static void main(String[] args)
{
Deque<String> element1=new Deque<String>();
Deque<String> element2=new Deque<String>();
for(int i=0;i<args.length;i++)
element1.addFirst(args[i]);
try {
for(;element1.numberOfItems+1>0;)
{
String temp=element1.removeFirst();
System.out.println(temp);
}
}
catch(Exception ex)
{
System.out.println("End Of Execution due to remove from empty queue");
}
System.out.println();
for(int i=0;i<args.length;i++)
element2.addLast(args[i]);
try {
for(;element2.numberOfItems+1>0;)
{
String temp=element2.removeLast();
System.out.println(temp);
}
}
catch(Exception ex)
{
System.out.println("End Of Execution due to remove from empty queue");
}
}
}

OUTPUT: