• A queue is a collection of items supportng three operations: – enqueue (item):
ID: 3683270 • Letter: #
Question
• A queue is a collection of items supportng three operations:
– enqueue (item): add item to the “front” of the queue
– dequeue(): removes the “last” item from the queue (the one
that’s been in the queue the longest) and returns it
– empty(): returns True if the stack is empty, else False
Note: stacks are “LIFO” (last-in-first-out), queues are “FIFO” (first-in-first-out)
Implement and test Queue class. Submit to dropbox: .py file containing Queue class and a funcGon testQueue() that demonstrates use of the class.
Explanation / Answer
import java.util.ArrayList;
import java.util.List;
public class DoubleEndedQueueImpl {
private List<Integer> deque = new ArrayList<Integer>();
public void insertFront(int item){
//add element at the beginning of the queue
System.out.println("adding at front: "+item);
deque.add(0,item);
System.out.println(deque);
}
public void insertRear(int item){
//add element at the end of the queue
System.out.println("adding at rear: "+item);
deque.add(item);
System.out.println(deque);
}
public void removeFront(){
if(deque.isEmpty()){
System.out.println("Deque underflow!! unable to remove.");
return;
}
//remove an item from the beginning of the queue
int rem = deque.remove(0);
System.out.println("removed from front: "+rem);
System.out.println(deque);
}
public void removeRear(){
if(deque.isEmpty()){
System.out.println("Deque underflow!! unable to remove.");
return;
}
//remove an item from the beginning of the queue
int rem = deque.remove(deque.size()-1);
System.out.println("removed from front: "+rem);
System.out.println(deque);
}
public int peakFront(){
//gets the element from the front without removing it
int item = deque.get(0);
System.out.println("Element at first: "+item);
return item;
}
public int peakRear(){
//gets the element from the rear without removing it
int item = deque.get(deque.size()-1);
System.out.println("Element at rear: "+item);
return item;
}
public static void main(String a[]){
DoubleEndedQueueImpl deq = new DoubleEndedQueueImpl();
deq.insertFront(34);
deq.insertRear(45);
deq.removeFront();
deq.removeFront();
deq.removeFront();
deq.insertFront(21);
deq.insertFront(98);
deq.insertRear(5);
deq.insertFront(43);
deq.removeRear();
}
}
output : -
adding at front: 34
[34]
adding at rear: 45
[34, 45]
removed from front: 34
[45]
removed from front: 45
[]
Deque underflow!! unable to remove.
adding at front: 21
[21]
adding at front: 98
[98, 21]
adding at rear: 5
[98, 21, 5]
adding at front: 43
[43, 98, 21, 5]
removed from front: 5
[43, 98, 21]
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.