Your task is to compute a set of all path lengths in a binary tree. For example, given this tree,


you should return the set {1, 3, 5 } because there are paths of length 1, 3, and 5 in this set. A path is a sequence of nodes starting from the root. The length of a path is the number of arrows in the figure, or equivalently, the number of nodes - 1.

You need to complete the recursive pathLengths method in the class below.

Complete the following file:

// TODO: Complete the pathLengths method in the Node class. import java.util.Set; import java.util.TreeSet; /** This class implements a binary search tree whose nodes hold objects that implement the Comparable interface. */ public class BinarySearchTree { // This method is used to check your work public static Set<Integer> check(String[] values) { BinarySearchTree tree = new BinarySearchTree(); for (String v : values) tree.add(v); return tree.pathLengths(); } /** Constructs an empty tree. */ public BinarySearchTree() { root = null; } public Set<Integer> pathLengths() { if (root == null) return null; return root.pathLengths(); } /** Inserts a new node into the tree. @param obj the object to insert */ public void add(Comparable obj) { Node newNode = new Node(); = obj; newNode.left = null; newNode.right = null; if (root == null) root = newNode; else root.addNode(newNode); } private Node root; /** A node of a tree stores a data item and references of the child nodes to the left and to the right. */ private class Node { public Set<Integer> pathLengths() { // TODO: Complete this method } /** Inserts a new node as a descendant of this node. @param newNode the node to insert */ public void addNode(Node newNode) { int comp =; if (comp < 0) { if (left == null) left = newNode; else left.addNode(newNode); } else if (comp > 0) { if (right == null) right = newNode; else right.addNode(newNode); } } public Comparable data; public Node left; public Node right; } }