Binary Search Tree(BST) in C++

#include<iostream>

using namespace std;

//Node class

class Node{

private:

int data;

Node* left;

Node* right;

friend class Tree;

public:

//constructors

Node(){

data=0;

left=right=NULL;

}

Node(int d){

data=d;

left=right=NULL;

}

};

//TREE

class Tree{

private:

Node* root;

public:

//INSERT function

Node* insert(Node* root, int data, bool a){

Node* ptr=new Node(data);

Node* temp_Root=NULL;

if(root==NULL){

root=ptr;

return root;

}

else if(a==0){

temp_Root=root->left=insert(root->left, data, a);

}

else{

temp_Root=root->right=insert(root->right, data, a);

}

return temp_Root;

}

//DISPLAY

void display_Post_Order(Node* root){

if(root==NULL)

return;

display_Post_Order(root->left);

display_Post_Order(root->right);

cout<<root->data<<" ";

}

};

//MAIN function

int main(){

//We create a pointer pointing that will point to a Node

Node* root;

//Initially(i.e tree is empty) root will be pointing to NULL

root=NULL;

Tree tree1;

root = tree1.insert(root, 2, 1);

Node* root_A=tree1.insert(root, 14, 0);

Node* root_B=tree1.insert(root, 5, 1);

Node* root_C=tree1.insert(root_A, 32, 0);

Node* root_D=tree1.insert(root_A, 44, 1);

Node* root_E=tree1.insert(root_B, 18, 0);

tree1.insert(root_B, 90, 1);

tree1.insert(root_C, 50, 0);

tree1.insert(root_C, 64, 1);

tree1.insert(root_D, 53, 0);

tree1.insert(root_D, 43, 1);

tree1.insert(root_E, 57, 0);

tree1.insert(root_E, 23, 1);

//display the contents of a BST in ascending order

tree1.display_Post_Order(root);

}