Construct BST from preorder traversal

#include<iostream>
using namespace std;
class Node{
  public:
      int data;
      Node *left,*right;
      Node(int key){
        data=key;
        left=right=NULL;
        }
  };

void Inorder(Node *root){
   if(root==NULL)
     return;
   Inorder(root->left);
   cout<<" "<<root->data;
   Inorder(root->right);
   }

void Insert(Node **root_ref,int key){
  if(*root_ref==NULL){
    *root_ref=new Node(key);
    return;
    }
  if((*root_ref)->data<key)
    Insert(&((*root_ref)->right),key);
  else
     if((*root_ref)->data>key)
       Insert(&((*root_ref)->left),key);
  }

int main(){
 cout<<"no. of nodes in tree";
 int n;
 cin>>n;
 int arr[n];
 cout<<endl<<"enter values in preorder :";
 for(int i=0;i<n;i++)
    cin>>arr[i];
 Node *root=NULL;
 for(int i=0;i<n;i++)
   Insert(&root,arr[i]);
 cout<<endl<<"Inorder of constructed BST tree is :";
 Inorder(root);
 return 0;
 }