public class TreeLevel {     public ListNode getTreeLevel(TreeNode root, int dep) {        // write code here        List
     
       result = new ArrayList();        ListNode res = null;        if(root == null || dep <= 0    ){            return res;        }        result.add(root);        if(dep == 1){            res = new ListNode(root.val);            return res;        }                while(dep > 1){            List
      
        temp = new ArrayList();            for(TreeNode t : result){                if(t.left != null) temp.add(t.left);                if(t.right != null) temp.add(t.right);            }            result = temp;            dep--;        }                res = new ListNode(result.get(0).val);        ListNode temp = res;        for(int i = 1; i < result.size(); i++){            temp.next = new ListNode(result.get(i).val);            temp = temp.next;        }        return res;    }}