//Calls a selection sort on the list
listNode* sort (listNode* head)
{
  if(head->next == NULL)
    return head;

  listNode* sortLead = head;
  listNode* smallest = sortLead;
  listNode* curr = sortLead->next;

  while(sortLead->next != NULL)
    {
      while(curr != NULL)
    {
      if(curr->data->freq < smallest->data->freq)
        {
          swap(curr, smallest);
        }
      curr = curr->next;
    }
      swap(sortLead, smallest);
      sortLead = sortLead->next;
      smallest = sortLead;
      curr = sortLead->next;
    }

  return head;
}