ou are given a linked list (head), where every element points to the root of an integer binary tree. Implement the method flatten which returns a binary tree from the values of all the trees, without duplicates, sorted by levels (while creating nodes by depth, from left to right).

For example, given the following list:

1 -> 4 -> 3 -> 6 \ / \
2 4 2 5 The method should return the following tree:

      1
   /     \
  2       3
 / \     /
4   5   6   

(since after removing duplicates & sorting we get the following elements: 1,2,3,4,5,6 and then fill up the tree by depth from left to right)

The classes ListNode & TreeNode are available for you:

class ListNode { public TreeNode data; public ListNode next;

ListNode(TreeNode data, ListNode next) { this.data = data; this.next = next; }

ListNode(TreeNode data) { this(data, null); } }

class TreeNode {

public TreeNode left; public TreeNode right; public int value;

TreeNode(int value, TreeNode left, TreeNode right) { this.value = value; this.left = left; this.right = right; }

TreeNode(int value) { this(value, null, null); } ... } This kata is sponsored by fun with trees & fun with lists collections!

Check out Fun with trees: lists edition as well!