C++ program to implement Binary Search Tree

/* C++ program for Binary Search Tree */

#include <iostream>
#include<cstdlib>

using namespace std;
class node
{
    public: int info;
            node *left,*right;
            friend class BST;
};

class BST
{
    public: node *getnode();
            node *create_bst_rec(node*,int);
            void postorder(node*);
            void preorder(node*);
            void inorder(node*);
};

node *BST :: getnode()
{
    node *p;
    p=new node;
    p->left=NULL;
    p->right=NULL;
    return(p);
}

node *BST :: create_bst_rec(node *t,int item)
{
    node *q;
    if(t==NULL)
    {
        q=getnode();
        q->info=item;
        t=q;
    }
    else
    {
        if(t->info==item)
        {
            cout<<"\n ITEM IS ALREADY EXIST...";
            return(t);
        }
        else if(t->info>item)
            t->left=create_bst_rec(t->left,item);
        else
            t->right=create_bst_rec(t->right,item);
    }
     return(t);
}

void BST :: postorder(node *t)
{
    if(t->left!=NULL)
       postorder(t->left);
    if(t->right!=NULL)
       postorder(t->right);
    cout<<"\t"<<t->info<<"  ";
}

void BST :: preorder(node *t)
{
    cout<<"\t"<<t->info<<"  ";
    if(t->left!=NULL)
       preorder(t->left);
    if(t->right!=NULL)
       preorder(t->right);
}

void BST :: inorder(node *t)
{
    if(t->left!=NULL)
       inorder(t->left);
    cout<<"\t"<<t->info<<"  ";
    if(t->right!=NULL)
       inorder(t->right);
}

int main()
{
    BST obj;
    node *n1=NULL;
    while(1)
    {
        cout<<"\n1.CREATE\n2.POSTORDER\n3.PREORDER\n4.INORDER\n5.EXIT";
        cout<<"\n Enter your choice:";
        int ch;
        cin>>ch;
        switch(ch)
        {
            case 1:cout<<"\n Enter data to insert: ";
                   int data;
                   cin>>data;
                   n1=obj.create_bst_rec(n1,data);
                   break;
            case 2:obj.postorder(n1);
                   break;
            case 3:obj.preorder(n1);
                   break;
            case 4:obj.inorder(n1);
                   break;
            case 5:exit(0);
            default:cout<<"\n wrong choice given";
        }
     }
     return(0);
}

Output