Java Program to Perform Deletion in a BST

This is a Java Program to perform deletion in the binary search tree.

Here is the source code of the Java Program to Perform Deletion in a BST. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

//This is a java program to delete elements from Binary Search Tree
import java.util.Random;
import java.util.Scanner;
 
class BSTNode
{
    BSTNode left, right;
    int     data;
 
    public BSTNode()
    {
        left = null;
        right = null;
        data = 0;
    }
 
    public BSTNode(int n)
    {
        left = null;
        right = null;
        data = n;
    }
 
    public void setLeft(BSTNode n)
    {
        left = n;
    }
 
    public void setRight(BSTNode n)
    {
        right = n;
    }
 
    public BSTNode getLeft()
    {
        return left;
    }
 
    public BSTNode getRight()
    {
        return right;
    }
 
    public void setData(int d)
    {
        data = d;
    }
 
    public int getData()
    {
        return data;
    }
}
 
class BSTree
{
    private BSTNode root;
 
    public BSTree()
    {
        root = null;
    }
 
    public boolean isEmpty()
    {
        return root == null;
    }
 
    public void insert(int data)
    {
        root = insert(root, data);
    }
 
    private BSTNode insert(BSTNode node, int data)
    {
        if (node == null)
            node = new BSTNode(data);
        else
        {
            if (data <= node.getData())
                node.left = insert(node.left, data);
            else
                node.right = insert(node.right, data);
        }
        return node;
    }
 
    public void delete(int k)
    {
        if (isEmpty())
            System.out.println("Tree Empty");
        else if (search(k) == false)
            System.out.println("Sorry " + k + " is not present");
        else
        {
            root = delete(root, k);
            System.out.println(k + " deleted from the tree");
        }
    }
 
    private BSTNode delete(BSTNode root, int k)
    {
        BSTNode p, p2, n;
        if (root.getData() == k)
        {
            BSTNode lt, rt;
            lt = root.getLeft();
            rt = root.getRight();
            if (lt == null && rt == null)
                return null;
            else if (lt == null)
            {
                p = rt;
                return p;
            } else if (rt == null)
            {
                p = lt;
                return p;
            } else
            {
                p2 = rt;
                p = rt;
                while (p.getLeft() != null)
                    p = p.getLeft();
                p.setLeft(lt);
                return p2;
            }
        }
        if (k < root.getData())
        {
            n = delete(root.getLeft(), k);
            root.setLeft(n);
        } else
        {
            n = delete(root.getRight(), k);
            root.setRight(n);
        }
        return root;
    }
 
    public boolean search(int val)
    {
        return search(root, val);
    }
 
    private boolean search(BSTNode r, int val)
    {
        boolean found = false;
        while ((r != null) && !found)
        {
            int rval = r.getData();
            if (val < rval)
                r = r.getLeft();
            else if (val > rval)
                r = r.getRight();
            else
            {
                found = true;
                break;
            }
            found = search(r, val);
        }
        return found;
    }
 
    public void inorder()
    {
        inorder(root);
    }
 
    private void inorder(BSTNode r)
    {
        if (r != null)
        {
            inorder(r.getLeft());
            System.out.print(r.getData() + " ");
            inorder(r.getRight());
        }
    }
 
    public void preorder()
    {
        preorder(root);
    }
 
    private void preorder(BSTNode r)
    {
        if (r != null)
        {
            System.out.print(r.getData() + " ");
            preorder(r.getLeft());
            preorder(r.getRight());
        }
    }
 
    public void postorder()
    {
        postorder(root);
    }
 
    private void postorder(BSTNode r)
    {
        if (r != null)
        {
            postorder(r.getLeft());
            postorder(r.getRight());
            System.out.print(r.getData() + " ");
        }
    }
}
 
public class Deletion_BST
{
    public static void main(String[] args)
    {
        BSTree bst = new BSTree();
        System.out.println("Binary Search Tree Deletion Test\n");
 
        Scanner sc = new Scanner(System.in);
        Random random = new Random();
        int n = 15;
        for (int i = 0; i < n; i++)
            bst.insert(Math.abs(random.nextInt(100)));
        char ch;
        do
        {
            System.out.print("\nPost order : ");
            bst.postorder();
            System.out.print("\nPre order  : ");
            bst.preorder();
            System.out.print("\nIn order   : ");
            bst.inorder();
 
            System.out.println("Enter integer element to delete");
            bst.delete(sc.nextInt());
            System.out.println("Continue deleting? <y>/<n>");
            ch = sc.next().charAt(0);
        } while (ch == 'y' || ch == 'Y');
        sc.close();
    }
}

Output:

$ javac Deletion_BST.java
$ java Deletion_BST
 
Binary Search Tree Deletion Test
 
 
Post order : 17 11 22 26 24 41 46 52 54 42 86 85 74 72 23 
Pre order  : 23 22 11 17 72 42 41 24 26 54 52 46 74 85 86 
In order   : 11 17 22 23 24 26 41 42 46 52 54 72 74 85 86 
Enter integer element to delete
17
17 deleted from the tree
Continue deleting? <y>/<n>
y
 
Post order : 11 22 26 24 41 46 52 54 42 86 85 74 72 23 
Pre order  : 23 22 11 72 42 41 24 26 54 52 46 74 85 86 
In order   : 11 22 23 24 26 41 42 46 52 54 72 74 85 86 
Enter integer element to delete
23
23 deleted from the tree
Continue deleting? <y>/<n>
y
 
Post order : 11 22 26 24 41 46 52 54 42 86 85 74 72 
Pre order  : 72 42 41 24 22 11 26 54 52 46 74 85 86 
In order   : 11 22 24 26 41 42 46 52 54 72 74 85 86 
Enter integer element to delete
11
11 deleted from the tree
Continue deleting? <y>/<n>
n