public class BinarySearchTree {

//Represent the node of binary tree

public static class Node{

int data;

Node left;

Node right;

public Node(int data){

//Assign data to the new node, set left and right children to null

this.data = data;

this.left = null;

this.right = null;

}

}

//Represent the root of binary tree

public Node root;

public BinarySearchTree(){

root = null;

}

//factorial() will calculate the factorial of given number

public int factorial(int num) {

int fact = 1;

if(num == 0)

return 1;

else {

while(num > 1) {

fact = fact * num;

num--;

}

return fact;

}

}

//numOfBST() will calculate the total number of possible BST by calculating Catalan Number for given key

public int numOfBST(int key) {

int catalanNumber = factorial(2 * key)/(factorial(key + 1) * factorial(key));

return catalanNumber;

}

public static void main(String[] args) {

BinarySearchTree bt = new BinarySearchTree();

//Display total number of possible binary search tree with key 5

System.out.println("Total number of possible Binary Search Trees with given key: " + bt.numOfBST(5));

}

}