Create a Linked List for each depth of a Binary Search Tree

LinkedListForEachDepth.java

import java.util.*;

public class LinkedListForEachDepth {

    public static void main(String[] args) {

        Node root = new Node(12);
        // ... create BST with nodes

        // create our list of LinkedLists
        ArrayList<LinkedList<Node>> lists = makeLinkedLists(root);
        
        // print them
        int count = 0;
        for (LinkedList<Node> ll : lists) {
            Iterator<Node> iter = ll.iterator();
            System.out.println("Linked list " + count++);
            while (iter.hasNext()) {
                System.out.print(iter.next() + " ");
            }
            System.out.println();
        }

    }

    public static ArrayList<LinkedList<Node>> makeLinkedLists(Node root) {
        LinkedList<Node> current = new LinkedList<Node>();
        LinkedList<Node> nextLevel = new LinkedList<Node>();
        ArrayList<LinkedList<Node>> lists = new ArrayList<LinkedList<Node>>();

        current.add(root);

        while (!current.isEmpty()) {
            LinkedList<Node> newLL = (LinkedList<Node>)current.clone();
            lists.add(newLL);
            
            while (!current.isEmpty()) {
                Node n = current.remove();
                if (n.left != null) nextLevel.add(n.left);
                if (n.right != null) nextLevel.add(n.right);
            }

            if (current.isEmpty()) {
                current = nextLevel;
                nextLevel = new LinkedList<Node>();
            }
        }
        return lists;
    }
    
}