Question

CAN SOMEONE PLEASE SOLVE THIS? THANK YOU.

FINALTREE.JAVA:

A leaf node is defined as a node in a tree that has no children. Given a BinarySearchTree write a method for the BST that returns a linked list of all leaves in ascending sorted order. The binary search tree's add method adds elements less than the parent to the left and elements greater than the parent to the right. If the tree is empty then an empty list should be returned Suppose the following elements are added to the tree from left to right. [50, 75, 85, 25] The resulting list returned by the method should contain [25, 85] The method should NOT return a linked list of the nodes of the tree but of the elements You are to use the following Java file which contains an implementation for a binary search tree, a main method for testing You may not modify anything pertaining to the add method, the constructor, isEmpty, or the Node class. You may only modify the main method for testing purposes and the method/methods you write except for the header of the getLeafElements method. This means you may not modify the return type, the method name, nor the number of parameters for getLeafElements. You may, however, write additional private helper methods to help you The Java file can be found here: Final Tree.java This problem can be solved recursively without additional data structures (other than those given). To receive full credit, you must implement a recursive method. If your algorithm is purely iterative, you will receive 85% credit.

import java.util.LinkedList;

public class FinalTree<E extends Comparable<? super E>> {

    private Node<E> root;
    private int size;
    
    public FinalTree() {
        root = null;
        size = 0;
    }
    
    public boolean isEmpty() {
        return size == 0;
    }
    
    public void add(E newItem) {
        if (isEmpty()) {
            root = new Node<E>(newItem);
        } else {
            Node<E> parent = null;
            Node<E> temp = root;
            int result = 0;
            while (temp != null) {
                parent = temp;
                result = newItem.compareTo(temp.data);
                if (result < 0) {
                    temp = temp.left;
                } else if (result > 0) {
                    temp = temp.right;
                } else {
                    return;
                }
            }
            if (result < 0) {
                parent.left = new Node<E>(newItem);
            } else if (result > 0) {
                parent.right = new Node<E>(newItem);
            }
        }
        size += 1;
    }
    
    /*****STUDENT CODE HERE*********************************************/
    
    public LinkedList<E> getLeafElements(){
        LinkedList<E> result = new LinkedList<E>();
        /***You may add code here******/
        
        
        
        /*********************************/
        return result;
    }
    
    /*******************************************************************/
    
    
    class Node<T>{
        Node<T> left;
        Node<T> right;
        T data;
        
        public Node(T data) {
            this.data = data;
        }
    }
    
    public static void main(String[] args) {
        FinalTree<String> ft1 = new FinalTree<String>();
        ft1.add("N");
        ft1.add("M");
        ft1.add("Q");
        ft1.add("G");
        ft1.add("H");
        ft1.add("A");
        ft1.add("D");
        ft1.add("T");
        ft1.add("S");
        ft1.add("R");
        ft1.add("P");
        ft1.add("O");
        System.out.println(ft1.getLeafElements()); //Should print [D, H, O, R]
        
        FinalTree<String> ft2 = new FinalTree<String>();
        System.out.println(ft2.getLeafElements()); //Should print []
    }
}

Answer 1

Given below is the completed code for the question.
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import java.util.LinkedList;

public class FinalTree<E extends Comparable<? super E>> {

private Node<E> root;
private int size;
  
public FinalTree() {
root = null;
size = 0;
}
  
public boolean isEmpty() {
return size == 0;
}
  
public void add(E newItem) {
if (isEmpty()) {
root = new Node<E>(newItem);
} else {
Node<E> parent = null;
Node<E> temp = root;
int result = 0;
while (temp != null) {
parent = temp;
result = newItem.compareTo(temp.data);
if (result < 0) {
temp = temp.left;
} else if (result > 0) {
temp = temp.right;
} else {
return;
}
}
if (result < 0) {
parent.left = new Node<E>(newItem);
} else if (result > 0) {
parent.right = new Node<E>(newItem);
}
}
size += 1;
}
  
/*****STUDENT CODE HERE*********************************************/
//helper method
private void getLeafElements(Node n, LinkedList<E> list){
if(n == null)
return;
else{
getLeafElements(n.left, list);
if(n.left == null && n.right == null)
list.add((E)n.data);
getLeafElements(n.right, list);
  
}
}
public LinkedList<E> getLeafElements(){
LinkedList<E> result = new LinkedList<E>();
/***You may add code here******/
getLeafElements(root, result);

/*********************************/
return result;
}
  
/*******************************************************************/
  
  
class Node<T>{
Node<T> left;
Node<T> right;
T data;
  
public Node(T data) {
this.data = data;
}
}
  
public static void main(String[] args) {
FinalTree<String> ft1 = new FinalTree<String>();
ft1.add("N");
ft1.add("M");
ft1.add("Q");
ft1.add("G");
ft1.add("H");
ft1.add("A");
ft1.add("D");
ft1.add("T");
ft1.add("S");
ft1.add("R");
ft1.add("P");
ft1.add("O");
System.out.println(ft1.getLeafElements()); //Should print [D, H, O, R]
  
FinalTree<String> ft2 = new FinalTree<String>();
System.out.println(ft2.getLeafElements()); //Should print []
}
}

output
-----
[D, H, O, R]
[]