struct node* copyList()
{
  //check if empty
  if(head==NULL){
  return NULL;}
  //create head
  struct node* p_head=head;//pointer to original head
  struct node* newHead = NULL; //head of new list
  struct node* p_newHead=newHead;//pointer to new head
  while(p_head!=NULL)
    int data=p_head->data;
    m_appendNode(data, p_newHead);
    p_head=p_head->next;
  }
  return newHead;
}

void m_appendNode(int data, struct node *newHead)
    {
    struct node* current=newHead;
    if(newHead!=NULL){
      while((current->next)!=NULL){
       current = current->next;
      }
      current->next=malloc(sizeof(struct node));
      current->next->data=data;
      current->next->next=NULL;
      }
    else{
      struct node* newnode=malloc(sizeof(struct node));
      newnode->data=data;
      newHead=newnode;
      newnode->next=NULL;
      }
    }