#### BST Recursive

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```package com.thealgorithms.datastructures.trees;

/**
*
*
* <h1>Binary Search Tree (Recursive)</h1>
*
* An implementation of BST recursively. In recursive implementation the checks
* are down the tree First root is checked if not found then its childs are
* checked Binary Search Tree is a binary tree which satisfies three properties:
* left child is less than root node, right child is grater than root node, both
* left and right childs must themselves be a BST.
*
* <p>
* I have made public functions as methods and to actually implement recursive
* approach I have used private methods
*
*/
public class BSTRecursive {

/**
* only data member is root of BST
*/
private Node root;

/**
* Constructor use to initialize node as null
*/
BSTRecursive() {
root = null;
}

/**
* main function for tests
*/
public static void main(String[] args) {
BSTRecursive tree = new BSTRecursive();
assert !tree.find(4) : "4 is not yet present in BST";
assert tree.find(10) : "10 should be present in BST";
tree.remove(9);
assert !tree.find(9) : "9 was just deleted from BST";
tree.remove(1);
assert !tree.find(
1
) : "Since 1 was not present so find deleting would do no change";
/*
Will print in following order
5 10 20 70
*/
tree.inorder();
}

/**
* Recursive method to delete a data if present in BST.
*
* @param node the current node to search for data
* @param data the value to be deleted
* @return Node the updated value of root parameter after delete operation
*/
private Node delete(Node node, int data) {
if (node == null) {
System.out.println("No such data present in BST.");
} else if (node.data > data) {
node.left = delete(node.left, data);
} else if (node.data < data) {
node.right = delete(node.right, data);
} else {
if (node.right == null && node.left == null) { // If it is leaf node
node = null;
} else if (node.left == null) { // If only right node is present
Node temp = node.right;
node.right = null;
node = temp;
} else if (node.right == null) { // Only left node is present
Node temp = node.left;
node.left = null;
node = temp;
} else { // both child are present
Node temp = node.right;
// Find leftmost child of right subtree
while (temp.left != null) {
temp = temp.left;
}
node.data = temp.data;
node.right = delete(node.right, temp.data);
}
}
return node;
}

/**
* Recursive insertion of value in BST.
*
* @param node to check if the data can be inserted in current node or its
* subtree
* @param data the value to be inserted
* @return the modified value of the root parameter after insertion
*/
private Node insert(Node node, int data) {
if (node == null) {
node = new Node(data);
} else if (node.data > data) {
node.left = insert(node.left, data);
} else if (node.data < data) {
node.right = insert(node.right, data);
}
return node;
}

/**
* Recursively print Preorder traversal of the BST
*
* @param node the root node
*/
private void preOrder(Node node) {
if (node == null) {
return;
}
System.out.print(node.data + " ");
if (node.left != null) {
preOrder(node.left);
}
if (node.right != null) {
preOrder(node.right);
}
}

/**
* Recursively print Postorder travesal of BST.
*
* @param node the root node
*/
private void postOrder(Node node) {
if (node == null) {
return;
}
if (node.left != null) {
postOrder(node.left);
}
if (node.right != null) {
postOrder(node.right);
}
System.out.print(node.data + " ");
}

/**
* Recursively print Inorder traversal of BST.
*
* @param node the root node
*/
private void inOrder(Node node) {
if (node == null) {
return;
}
if (node.left != null) {
inOrder(node.left);
}
System.out.print(node.data + " ");
if (node.right != null) {
inOrder(node.right);
}
}

/**
* Serach recursively if the given value is present in BST or not.
*
* @param node the current node to check
* @param data the value to be checked
* @return boolean if data is present or not
*/
private boolean search(Node node, int data) {
if (node == null) {
return false;
} else if (node.data == data) {
return true;
} else if (node.data > data) {
return search(node.left, data);
} else {
return search(node.right, data);
}
}

/**
* add in BST. if the value is not already present it is inserted or else no
* change takes place.
*
* @param data the value to be inserted
*/
this.root = insert(this.root, data);
}

/**
* If data is present in BST delete it else do nothing.
*
* @param data the value to be removed
*/
public void remove(int data) {
this.root = delete(this.root, data);
}

/**
* To call inorder traversal on tree
*/
public void inorder() {
System.out.println("Inorder traversal of this tree is:");
inOrder(this.root);
System.out.println(); // for next line
}

/**
* To call postorder traversal on tree
*/
public void postorder() {
System.out.println("Postorder traversal of this tree is:");
postOrder(this.root);
System.out.println(); // for next li
}

/**
* To call preorder traversal on tree.
*/
public void preorder() {
System.out.println("Preorder traversal of this tree is:");
preOrder(this.root);
System.out.println(); // for next li
}

/**
* To check if given value is present in tree or not.
*
* @param data the data to be found for
*/
public boolean find(int data) {
if (search(this.root, data)) {
System.out.println(data + " is present in given BST.");
return true;
}
return false;
}

/**
* The Node class used for building binary search tree
*/
private static class Node {

int data;
Node left;
Node right;

/**
* Constructor with data as parameter
*/
Node(int d) {
data = d;
left = null;
right = null;
}
}
}
```