John John - 4 months ago 19
Java Question

BinaryTree implementation in java

I have this code for BinaryTree creation and traversal


class Node
{
Integer data;
Node left;
Node right;
Node()
{
data = null;
left = null;
right = null;
}
}
class BinaryTree
{
Node head;
Scanner input = new Scanner(System.in);
BinaryTree()
{
head = null;
}
public void createNode(Node temp, Integer value)
{
Node newnode= new Node();
value = getData();
newnode.data = value;
temp = newnode;
if(head==null)
{
head = temp;
}
System.out.println("If left child exits for ("+value+") enter y else n");
if(input.next().charAt(0)=='y')
{
createNode(temp.left, value);
}
System.out.println("If right child exits for ("+value+") enter y else n");
if(input.next().charAt(0)=='y')
{
createNode(temp.right, value);
}
}
public Integer getData()
{
out.println("Enter the value to insert:");
return (Integer)input.nextInt();
}

public void print()
{
inorder(head);
}
public void inorder(Node node)
{
if(node!=null)
{
inorder(node.left);
System.out.println(node.data);
inorder(node.right);
}
else
return;
}
}

class BinaryTreeWorker
{
static BinaryTree treeObj = null;
static Scanner input = new Scanner(System.in);
public static void displaymenu()
{
int choice;
do{
out.print("\n Basic operations on a tree:");
out.print("\n 1. Create tree \n 2. Insert \n 3. Search value \n 4. print list\n Else. Exit \n Choice:");
choice = input.nextInt();

switch(choice)
{
case 1:
treeObj = createBTree();
break;
case 2:
treeObj.createNode(null, null);
break;
case 3:
//searchnode();
break;
case 4:
treeObj.print();
break;
default:
return;
}
}while(true);
}
public static BinaryTree createBTree()
{
return new BinaryTree();
}
public static void main(String[] args)
{
displaymenu();
}
}


It compiles and runs. But I think there is something wrong with the inorder traversal.

I created the below tree,


2
1 3


But it prints only 2.

Answer

I have tried solving the problem your way and I have pasted the solution below.. Though I haven't tested it thoroughly so it might fail in some edge condition.. But I have tested it for one case. Kindly let me know if it fails in some scenario. I would appreciate others help in making this answer better. I agree that this solution is not the most ideal way to code a Binary Tree but it wont hurt this way if some one is just practicing..

import java.util.Scanner;


class Node
{
    Integer data;
    Node left;
    Node right;
    Node()
    {
        data = null;
        left = null;
        right = null;
    }
}
class BinaryTree
{
    Node head;
    Scanner input = new Scanner(System.in);
    BinaryTree()
    {
        head = null;
    }

    public void createNode(Node temp,Node newnode) 
    {

        if(head==null)
        {
            System.out.println("No value exist in tree, the value just entered is set to Root");
            head = newnode;
            return;
        }
        if(temp==null)
            temp = head;

        System.out.println("where you want to insert this value, l for left of ("+temp.data+") ,r for right of ("+temp.data+")");
        char inputValue=input.next().charAt(0); 
        if(inputValue=='l'){
            if(temp.left==null)
            {
                temp.left=newnode;
                System.out.println("value got successfully added to left of ("+temp.data+")");
                return;
            }else  {
                System.out.println("value left to ("+temp.data+") is occupied 1by ("+temp.left.data+")");
                createNode(temp.left,newnode);
            }
        }
        else if(inputValue=='r')
        {
            if(temp.right==null)
            {
                temp.right=newnode;
                System.out.println("value got successfully added to right of ("+temp.data+")");
                return;

            }else  {
                System.out.println("value right to ("+temp.data+") is occupied by ("+temp.right.data+")");
                createNode(temp.right,newnode);
            }

        }else{
            System.out.println("incorrect input plz try again , correctly");
            return;
        }

    }
    public Node generateTree(){
        int [] a = new int[10];
        int index = 0; 
        while(index<a.length){
            a[index]=getData();
            index++;
        }
        if(a.length==0 ){
            return null;
        }
        Node newnode= new Node();
        /*newnode.left=null;
        newnode.right=null;*/
        return generateTreeWithArray(newnode,a,0);

    }
    public Node generateTreeWithArray(Node head,int [] a,int index){

        if(index >= a.length)
            return null;
        System.out.println("at index "+index+" value is "+a[index]);
        if(head==null)
            head= new Node();
        head.data = a[index];
        head.left=generateTreeWithArray(head.left,a,index*2+1);
        head.right=generateTreeWithArray(head.right,a,index*2+2);
        return head;
    }

    public Integer getData()
    {
        System.out.println("Enter the value to insert:");
        return (Integer)input.nextInt();
    }

    public void print()
    {
        inorder(head);
    }
    public void inorder(Node node)
    {
        if(node!=null)
        {
            inorder(node.left);
            System.out.println(node.data);
            inorder(node.right);
        }
        else
            return;
    }
}

public class BinaryTreeWorker
{
    static BinaryTree treeObj = null;
    static Scanner input = new Scanner(System.in);
    public static void displaymenu()
    {
        int choice;
        do{
            System.out.print("\n Basic operations on a tree:");
            System.out.print("\n 1. Create tree  \n 2. Insert \n 3. Search value \n 4. print list\n 5. generate a tree \n Else. Exit \n Choice:");
            choice = input.nextInt();

            switch(choice)
            {
                case 1:
                    treeObj = createBTree();
                    break;
                case 2:
                    Node newnode= new Node();
                    newnode.data = getData();
                    newnode.left=null;
                    newnode.right=null;
                    treeObj.createNode(treeObj.head,newnode);
                    break;
                case 3:
                    //searchnode();
                    break;
                case 4:
                    System.out.println("inorder traversal of list gives follows");
                    treeObj.print();
                    break;
                case 5:
                    Node tempHead = treeObj.generateTree();
                    System.out.println("inorder traversal of list with head = ("+tempHead.data+")gives follows");
                    treeObj.inorder(tempHead);
                    break;
                default:
                    return;
            }       
        }while(true);
    }
    public static Integer getData()
    {
        System.out.println("Enter the value to insert:");
        return (Integer)input.nextInt();
    }
    public static BinaryTree createBTree()
    {
        return new BinaryTree();
    }
    public static void main(String[] args)
    {
        displaymenu();
    }
}

[Update] : Updated the code to generate a binary tree using an array. This will involve less user interaction.

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