Distance between two nodes of binary search tree.

public class BSTextends Comparablesuper T>> implements BSTInterface { // DO NOT ADD OR MODIFY INSTANCE VARIABLES.  private BSTNode root; private int size; /**  * A no-argument constructor that should initialize an empty BST.  * DO NOT IMPLEMENT THIS CONSTRUCTOR!  */  public BST() { size = 0; root = null; } 

....

...

...

...

/**  * Calculates the shortest distance between two elements in the tree.  *  * To do this, you must first find the deepest common ancestor of both data.  * From there, find {@code data1} and {@code data2} in the BST, counting up  * the number of nodes it took to get there. Please note that there  * is no relationship between the data parameters in that they may not  * belong to the same branch. You will most likely have to split off and  * traverse the tree for each piece of data.  *  * This method should only need to traverse to the deepest common ancestor  * once, and from that node to each data in one traversal each. Failure to  * do so will result in an efficiency penalty.  *  * EXAMPLE: Given the BST below composed of Integers:  *  * 50  * / \  * 25 75  * / \  * 12 37  * / \ \  * 10 15 40  * /  * 13  *  * distanceBetween(40, 13) should return 5.  * distanceBetween(37, 37) should return 0.  * distanceBetween(25, 37) should return 1.  *  * Should have a running time of O(log n) for a balanced tree, and a worst  * case of O(n).  *  * @param data1 the data to start the path from  * @param data2 the data to end the path on  * @return the shortest distance between the two data in the tree  * @throws IllegalArgumentException if either data1 or data2 is null  * @throws java.util.NoSuchElementException if data1 or data2 is not in  * the tree  */ @Override public int distance(T data1, T data2) { } 

...

...

.

...

..

public class BSTNodeextends Comparablesuper T>> { private T data; private BSTNode left; private BSTNode right; /**  * Create a BST node with the given data.  *  * @param data the data to be stored in this node.  */  public BSTNode(T data) { this.data = data; } /**  * Get the data in this node.  *  * @return data in this node.  */  public T getData() { return data; } /**  * Set the data in this node.  *  * @param data data to be placed into the node.  */  public void setData(T data) { this.data = data; } /**  * Get the node to the left of this node.  *  * @return node to the left.  */  public BSTNode getLeft() { return left; } /**  * Set the node to the left of this node.  *  * @param left new node to the left.  */  public void setLeft(BSTNode left) { this.left = left; } /**  * Get the node to the right of this node.  *  * @return node to the right.  */  public BSTNode getRight() { return right; } /**  * Set the node to the right of this node.  *  * @param right new node to the right.  */  public void setRight(BSTNode right) { this.right = right; } }