BinarySearchTree.java

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));  
      }  
}