static void tdefl_calculate_minimum_redundancy(tdefl_sym_freq *A, int n) {
  int root, leaf, next, avbl, used, dpth;
  if (n == 0)
    return;
  else if (n == 1) {
    A[0].m_key = 1;
    return;
  }
  A[0].m_key += A[1].m_key;
  root = 0;
  leaf = 2;
  for (next = 1; next < n - 1; next++) {
    if (leaf >= n || A[root].m_key < A[leaf].m_key) {
      A[next].m_key = A[root].m_key;
      A[root++].m_key = (mz_uint16)next;
    } else
      A[next].m_key = A[leaf++].m_key;
    if (leaf >= n || (root < next && A[root].m_key < A[leaf].m_key)) {
      A[next].m_key = (mz_uint16)(A[next].m_key + A[root].m_key);
      A[root++].m_key = (mz_uint16)next;
    } else
      A[next].m_key = (mz_uint16)(A[next].m_key + A[leaf++].m_key);
  }
  A[n - 2].m_key = 0;
  for (next = n - 3; next >= 0; next--)
    A[next].m_key = A[A[next].m_key].m_key + 1;
  avbl = 1;
  used = dpth = 0;
  root = n - 2;
  next = n - 1;
  while (avbl > 0) {
    while (root >= 0 && (int)A[root].m_key == dpth) {
      used++;
      root--;
    }
    while (avbl > used) {
      A[next--].m_key = (mz_uint16)(dpth);
      avbl--;
    }
    avbl = 2 * used;
    dpth++;
    used = 0;
  }
}