import java.util.Iterator;
import java.util.Random;

public class ListWithLoopDetection<Item> implements Iterable<Item> {
    
    public static final int MAX_ITEMS_TO_PRINT = 30;
    
    private class Node<Item> {
        Item item;
        Node<Item> next;
    }
    
    // YOU MAY ADD EXACTLY ONE INSTANCE VARIABLE, IF NEEDED
 
    public void addItem(Item item) {
        // ADD CODE HERE 
    }
    
    public void insertLoopToPosition(int pos) {
        // ADD CODE HERE
    }
    
    // YOU MAY ADD EXACTLY ONE ADDITIONAL METHOD HERE, IF NEEDED
    
    public boolean loopExists() {
        // ADD CODE HERE
    }
    
    public static void main(String[] args) {
        Random random = new Random();
        
        // Your code must NOT rely on this to work, but we choose 
        // to test the code with lists small enough that when
        // printed, it will be obvious if a loop exists
        int numItems = 1 + random.nextInt(MAX_ITEMS_TO_PRINT / 2);
        
        // make list of n integers (0 through (n-1))
        ListWithLoopDetection<Integer> list = new ListWithLoopDetection<Integer>();
        for (int i = 0; i < numItems; i++) {
            list.addItem(i);
        }

        // half of the time (at random) put in a loop
        if (random.nextBoolean()) {  
            list.insertLoopToPosition(random.nextInt(numItems));
        }
        
        // print the list
        int count = 0;
        for (Integer i : list) {
            if (count > MAX_ITEMS_TO_PRINT) {
                System.out.print("...");
                break;
            }
            System.out.printf("%d ",i);
            count++;
        }
        System.out.println();
        
        // detect a loop, if present
        System.out.println(list.loopExists() ? "Loop Exists" : "No Loop Exists");
    }
}