Question

You will be traversing through an integer tree to print the data. Given main(), write the methods in the 'IntegerBinaryTree' class specified by the // TODO: sections. There are 6 methods in all to write.

Ex: If the input is

70
86
60
90
49
62
81
85
38
-1

the output should be:

Enter whole numbers to insert into the tree, -1 to stop

Inorder: 38 - 49 - 60 - 62 - 70 - 81 - 85 - 86 - 90 - 

Reverse Preorder: 70 - 86 - 90 - 81 - 85 - 60 - 62 - 49 - 38 - 

Reverse Postorder: 90 - 85 - 81 - 86 - 62 - 38 - 49 - 60 - 70 - 

Main.java

import java.util.Scanner;

public class Main {

   public static void main(String[] args) {
      
       IntegerBinaryTree tree = new IntegerBinaryTree();
      
       Scanner scrn = new Scanner(System.in);
       System.out.println("Enter whole numbers to insert into the tree, -1 to stop");
      
       int num = scrn.nextInt();
       while(num != -1) {
           tree.insertNode(num);
           num = scrn.nextInt();
       }
       System.out.println();
      
       tree.printInorder();
       tree.printReversePreorder();
       tree.printReversePostorder();

   }

}

Node.java

public class Node {

   private int element;
   private Node left;
   private Node right;
  
   public Node(int ele) {
       element = ele;
       this.left = null;
       this.right = null;
   }
  
   public int getElement() {
       return element;
   }
  
   public Node getLeft() {
       return left;
   }
  
   public Node getRight() {
       return right;
   }
  
   public void setLeft(Node Left) {
       left = Left;
   }
  
   public void setRight(Node Right) {
       right = Right;
   }
}

IntegerBinaryTree.java

public class IntegerBinaryTree {

   private Node root = null;
  
   public void insertNode(int value) {
       if (root == null) { // empty, so make root node
           root = new Node(value);
       }
       else {
           Node pos = root;
           while(pos != null) {
               if (value < pos.getElement()) {
                   if (pos.getLeft() == null) {
                       pos.setLeft(new Node(value));
                       pos = null;
                   }
                   else {
                       pos = pos.getLeft();
                   }
               }
               else {
                   if (pos.getRight() == null) {
                       pos.setRight(new Node(value));
                       pos = null;
                   }
                   else {
                       pos = pos.getRight();
                   }
               }
           }
       }
   }
  
   // TODO: write the method printInorder
       // It should check that the tree isn't empty
       // and prints "Tree is empty" if it is
       // otherwise prints "Inorder: ", calls the Inorder method,
       // and prints an empty line
      

  
  
   // TODO: write the method printReversePreorder
       // It should check that the tree isn't empty
       // and prints "Tree is empty" if it is
       // otherwise prints "ReversePreorder: ", calls the reversePreorder method,
   // and prints an empty line

   // TODO: write the method printReversePostorder
       // It should check that the tree isn't empty
       // and prints "Tree is empty" if it is
       // otherwise prints "ReversePreorder: ", calls the reversePostorder method,
// and prints an empty line

  
   // TODO: write the inorder method
   // that traverses the tree and prints the data inorder

  
   // TODO: write the method reversePreorder
   // that traverses the tree and prints the data in reverse Preorder (right before left)
  

   // TODO: write the method reversePostorder
       // that traverses the tree and prints the data in reverse Postorder (right before left)

}

Answer 1

code after implementation

IntegerBinaryTree.java (code to copy)

public class IntegerBinaryTree {

   private Node root = null;
  
   public void insertNode(int value) {
       if (root == null) { // empty, so make root node
           root = new Node(value);
       }
       else {
           Node pos = root;
           while(pos != null) {
               if (value < pos.getElement()) {
                   if (pos.getLeft() == null) {
                       pos.setLeft(new Node(value));
                       pos = null;
                   }
                   else {
                       pos = pos.getLeft();
                   }
               }
               else {
                   if (pos.getRight() == null) {
                       pos.setRight(new Node(value));
                       pos = null;
                   }
                   else {
                       pos = pos.getRight();
                   }
               }
           }
       }
   }
   // TODO: write the method printInorder
       // It should check that the tree isn't empty
       // and prints "Tree is empty" if it is
       // otherwise prints "Inorder: ", calls the Inorder method,
       // and prints an empty line
   public void printInorder(){
       if(root==null){
           System.out.println("Tree is empty");
       }else{
           System.out.print("Inorder: ");
           inorder(root);
           System.out.println();
       }
   }
   
    // TODO: write the method printReversePreorder
       // It should check that the tree isn't empty
       // and prints "Tree is empty" if it is
       // otherwise prints "ReversePreorder: ", calls the reversePreorder method,
   // and prints an empty line 
   public void printReversePreorder(){
       if(root==null){
           System.out.println("Tree is empty");
       }else{
           System.out.print("ReversePreorder: ");
           reversePreorder(root);
           System.out.println();
       }
   }

   // TODO: write the method printReversePostorder
       // It should check that the tree isn't empty
       // and prints "Tree is empty" if it is
       // otherwise prints "ReversePreorder: ", calls the reversePostorder method,
// and prints an empty line
    public void printReversePostorder(){
        if(root==null){
            System.out.println("Tree is empty");
        }else{
            System.out.print("ReversePreorder: ");
            reversePostorder(root);
            System.out.println();
        }
    }

  // TODO: write the inorder method
   // that traverses the tree and prints the data inorder
    private void inorder(Node root){
        if(root==null)
            return;
        inorder(root.getLeft());
        System.out.print(root.getElement()+" -");
        inorder(root.getRight());
    }
   
   // TODO: write the method reversePreorder
   // that traverses the tree and prints the data in reverse Preorder (right before left)
    private void reversePreorder(Node root){
        if(root==null)
            return;
        System.out.print(root.getElement()+" -");
        reversePreorder(root.getRight());
        reversePreorder(root.getLeft());
    }
  

   // TODO: write the method reversePostorder
       // that traverses the tree and prints the data in reverse Postorder (right before left)
    private void reversePostorder(Node root){
        if(root==null)
            return;
        reversePostorder(root.getRight());
        reversePostorder(root.getLeft());
        System.out.print(root.getElement()+" -");
    }

}

IntegerBinaryTree.java code screenshot

Input/Output Screenshot after running Main.java