import java.util.List;

/**
 * Represents a single node in a tree.
 */
public interface TreeNode {

   /**
    * @return This node's element
    */
   public int getElement();

   /**
    * Set this node's element to the argument.
    * @param i The element encapsulated by this node.
    */
   public void setElement(int i);

   /**
    * @return This node's parent.
    */
   public TreeNode getParent();

   /**
    * @return All of this node's direct descendents
    */
   public List<TreeNode> getChildren();

   /**
    * Makes the given node a child of this node.
    * @param child  The node to add as a child.
    */
   public void addChild(TreeNode child);

   /**
    * @return The number of nodes belonging to this node's subtree, including
    *         this node.
    */
   public int size();

   /**
    * @return The height of this node in the tree.
    *
    * The height of any node is 1 more than the height of its maximum-height
    * child.
    */
   public int height();

   /**
    * Displays all the elements in the subtree rooted at this node in
    * an order that ensures parents are displayed before any of their 
    * children have been displayed.
    */
   public void printPreOrder();

   /**
    * Displays all the elements in the subtree rooted at this node in
    * an order that ensures parents are displayed after all their 
    * children have been displayed.
    */
   public void printPostOrder();
}