C++ program to append the last n nodes of a linked list to the beginning of the list

Run

#include<iostream>
using namespace std;
class node
{
public:
  int data;
  node *next;

  //Constructor 
    node (int d)
  {
    data = d;
    next = NULL;
  }
};
void insertAtTail (node * &head, int data)	//function to insert new element at tail of the list
{
  if (head == NULL)
    {
      head = new node (data);
      return;
    }
  node *tail = head;
  while (tail->next != NULL)
    {
      tail = tail->next;
    }
  tail->next = new node (data);
}

int buildList (node * &head)	//function to build the list.
{
  int n;
  cout << "Enter the size of list:"; cin >> n;
  cout << endl;
  int a = n;
  cout << "Enter data of the nodes\n"; while (n--) { int data; cin >> data;
      insertAtTail (head, data);	//New element will be inserted at end.
    }
  return a;
}

void display (node * node)
{

  // as linked list will end when Node is Null
  while (node != NULL)
    {
      printf ("%d ", node->data);
      node = node->next;
    }
}

node *append (node * head, int k, int n)	//function to find last n nodes
{
  node *last;
  last = head;
  int i = 0;
  int ok = n - k - 1;
  while (last != NULL && i < ok) { last = last->next;
      i++;
    }
  node *second = last->next;
  last->next = NULL;
  return second;
}

int main ()				//main function
{
  int k;
  node *head = NULL;
  int n = buildList (head);
  cout << "Linked list data: ";
  display (head);
  cout << "\nEnter the value of 'n': "; cin >> k;
  node *temp = append (head, k, n);
  cout <<
    "\nAfter appending the last n nodes of a linked list to the beginning of the list\n";
  cout << "Linked list data: ";
  display (temp);		// printing last n nodes
  display (head);		//printing remaining nodes
}