Question

I have a Java Data Structures project and we're creating a linked list and an iterator for that linked list. The add method for the linked list has to be O(1). This is my code

public class MyLinkedList extends CS20bLinkedList implements Iterable<Integer> {
  
    @Override
     public void add(int value){
       
      
        Node tail = head;
  
        if(head == null){
          
            head = new Node(value);
            //System.out.println("Very Fun! "+head.value);
          
            return;
      
        }else{
          
            tail.next = new Node(value);
            //System.out.println("Very Fun! "+head.value);
            //System.out.println("Very Fun! "+tail.value);
            //System.out.println("Very Funny "+tail.next.value);
            tail = tail.next;
  
        }

public class MyIterator extends MyLinkedList implements Iterator<Integer> {
  
    Node temp;
  
    MyIterator(Node head){
  
        temp = head;
  
    }
  
    @Override
    public boolean hasNext() {
      
      
        return temp == null;
      
    }

    @Override
    public Integer next() {
      
        Integer item;
      
        item = temp.value;
      
        temp = temp.next;
     
        return item;
      
      
      
    }
      
  
}

  
        }

        @Override
        public Iterator<Integer> iterator() {
      
            return new MyIterator(head);
        }
  
  
  
  
}

I'm pretty sure the problem with my linked list is that every time the add method gets called it the tail node gets reset and it becomes equal to the head node. I need the tail node to make the add method O(1) instead of O(N). How do I give a value to tail without having it reset every time the add method gets called?

Answer 1

Hi I have added some comments apart from that your code is fine. In case of any doubts please comment

public class MyLinkedList extends CS20bLinkedList implements Iterable<Integer> {
  
@Override
public void add(int value){

  
//Node tail = head;//this statement is wrong here tail is also for whole linked list so like head, tail also to be declared where head has been declared
  
if(head == null){
  
head = new Node(value);
//System.out.println("Very Fun! "+head.value);
//here since head is null so there is no no node in the list and now we are adding one node so head and tail points to same node here following statement has to be added
tail=head;
return;
  
}else{
  
tail.next = new Node(value);
//System.out.println("Very Fun! "+head.value);
//System.out.println("Very Fun! "+tail.value);
//System.out.println("Very Funny "+tail.next.value);
tail = tail.next;
  
}

public class MyIterator extends MyLinkedList implements Iterator<Integer> {
  
Node temp;
  
MyIterator(Node head){
  
temp = head;
  
}
  
@Override
public boolean hasNext() {
  
  
return temp == null;
  
}

@Override
public Integer next() {
  
Integer item;
  
item = temp.value;
  
temp = temp.next;

return item;
  
  
  
}
  
  
}

  
}

@Override
public Iterator<Integer> iterator() {
  
return new MyIterator(head);
}
  
  
  
  
}