Insertion at Beginning in Doubly Linked list in C++

Run

#include<iostream>
using namespace std;

struct node
{
  int num;
  struct node *preptr;
  struct node *nextptr;
} *stnode, *ennode;


void DlListcreation (int n);
void DlLinsertNodeAtBeginning (int num);
void displayDlList ();

int main ()
{
  int n, num1;
  stnode = NULL;
  ennode = NULL;

  cout << "Enter the number of nodes : "; cin >> n;
  DlListcreation (n);
  displayDlList ();
  cout << " Input data for insertion at beginning : "; cin >> num1;
  DlLinsertNodeAtBeginning (num1);
  displayDlList ();
  return 0;
}

void DlListcreation (int n)
{
  int i, num;
  struct node *fnNode;

  if (n >= 1)
    {
      stnode = (struct node *) malloc (sizeof (struct node));

      if (stnode != NULL)
	{
	  cout << " Input data for node 1 : "; // assigning data in the first node cin >> num;

	  stnode->num = num;
	  stnode->preptr = NULL;
	  stnode->nextptr = NULL;
	  ennode = stnode;
	  for (i = 2; i <= n; i++)
	    {
	      fnNode = (struct node *) malloc (sizeof (struct node));
	      if (fnNode != NULL)
		{
		  cout << " Input data for node " << i << ": "; cin >> num;
		  fnNode->num = num;
		  fnNode->preptr = ennode;	// new node is linking with the previous node
		  fnNode->nextptr = NULL;

		  ennode->nextptr = fnNode;	// previous node is linking with the new node
		  ennode = fnNode;	// assign new node as last node
		}
	      else
		{
		  cout << " Memory can not be allocated.";
		  break;
		}
	    }
	}
      else
	{
	  cout << " Memory can not be allocated.";
	}
    }
}

void DlLinsertNodeAtBeginning (int num)
{
  struct node *newnode;
  if (stnode == NULL)
    {
      cout << " No data found in the list\n"; } else { newnode = (struct node *) malloc (sizeof (struct node)); newnode->num = num;
      newnode->nextptr = stnode;	// next address of new node is linking with starting node
      newnode->preptr = NULL;	// set previous address field of new node is NULL
      stnode->preptr = newnode;	// previous address of starting node is linking with new node
      stnode = newnode;		// set the new node as starting node
    }
}

void displayDlList ()
{
  struct node *tmp;
  tmp = stnode;
  int n = 1;
  while (tmp != NULL)
    {
      cout << " node " << n << ": " << tmp->num << "\n"; n++; tmp = tmp->nextptr;	// current pointer moves to the next node
    }
}