const int maxcount = 19;
  int distrib[maxcount + 2];
  int uniques = 0;
  bzero(distrib, sizeof(distrib));

  for (int i = 0; i < tabsize; i += 1)
  { int len = 0;
    entry * ptr = hashtable[i];
    while (ptr != NULL)
    { uniques += 1;
      len += 1;
      ptr = ptr->next; }
    if (len <= maxcount)
      distrib[len] += 1;
    else
      distrib[maxcount + 1] += 1; }

  double lambda = uniques / (double)tabsize;
  double expect = exp(- lambda) * tabsize;

  for (int i = 0; i <= maxcount + 1; i += 1)
  { cout << setw(2) << i << ": " 
         << setw(10) << distrib[i]
         << " expect " << (int)expect << "\n";
    expect = expect * lambda / (i + 1); }
  cout << "> : " << distrib[20] << "\n";