video 1 intro of binary search tree (love babbar)

#include<iostream>
#include<queue>
using namespace std;
class node {
    public:
        int data;
        node* left;
        node* right;
    node(int d) {
        this -> data = d;
        this -> left = NULL;
        this -> right = NULL;
    }
};
node* buildTree(node* root) {
    cout << "Enter the data: " << endl;
    int data;
    cin >> data;
    root = new node(data);    
    if(data == -1) {
        return NULL;
    }
    cout << "Enter data for inserting in left of " << data << endl;
    root->left = buildTree(root->left);
    cout << "Enter data for inserting in right of " << data << endl;
    root->right = buildTree(root->right);
    return root;
}
void levelOrderTraversal(node* root) {
    queue<node*> q;
    q.push(root);
    q.push(NULL);
    while(!q.empty()) {
        node* temp = q.front();
        q.pop();
        if(temp == NULL) { 
            //purana level complete traverse ho chuka hai
            cout << endl;
            if(!q.empty()) { 
                //queue still has some child ndoes
                q.push(NULL);
            }  
        }
        else{
            cout << temp -> data << " ";
            if(temp ->left) {
                q.push(temp ->left);
            }
            if(temp ->right) {
                q.push(temp ->right);
            }
        }
    }
}
void inorder(node* root) {
    //base case
    if(root == NULL) {
        return ;
    }
    inorder(root->left);
    cout << root-> data << " ";
    inorder(root->right);
}
void preorder(node* root) {
    //base case
    if(root == NULL) {
        return ;
    }
    cout << root-> data << " ";
    preorder(root->left);
    preorder(root->right);
}
void postorder(node* root) {
    //base case
    if(root == NULL) {
        return ;
    }
    postorder(root->left);
    postorder(root->right);
    cout << root-> data << " ";
}
void buildFromLevelOrder(node* &root) {
    queue<node*> q;
    cout << "Enter data for root" << endl;
    int data ;
    cin >> data;
    root = new node(data);
    
    q.push(root);
    while(!q.empty()) {
        node* temp = q.front();
        q.pop();
        cout << "Enter left node for: " << temp->data << endl;
        int leftData;
        cin >> leftData;
        if(leftData != -1) {
            temp -> left = new node(leftData);
            q.push(temp->left);
        }
        cout << "Enter right node for: " << temp->data << endl;
        int rightData;
        cin >> rightData;
        if(rightData != -1) {
            temp -> right = new node(rightData);
            q.push(temp->right);
        }
    }
 }
int main() {
    node* root = NULL;
    buildFromLevelOrder(root);
    levelOrderTraversal(root);
    // 1 3 5 7 11 17 -1 -1 -1 -1 -1 -1 -1
    /*
    //creating a Tree
    root = buildTree(root);
    //1 3 7 -1 -1 11 -1 -1 5 17 -1 -1 -1 
    //level order
    cout << "Printing the level order tracersal output " << endl;
    levelOrderTraversal(root);
    cout << "inorder traversal is:  ";
    inorder(root); 
    cout << endl << "preorder traversal is:  ";
    preorder(root); 
    cout << endl << "postorder traversal is:  ";
    postorder(root); 
    */
    return 0;
}