These are not the algorithms but an overview of the formulas.

For example the HN algorithm is outlined in several places e.g. http://news.ycombinator.com/item?id=38704 and on the pg Arc site, and the reddit algorithms is

  def hot(ups, downs, date):
  s = score(ups, downs)
  order = log(max(abs(s), 1), 10)
  sign = 1 if s > 0 else -1 if s < 0 else 0
  seconds = epoch_seconds(date) - 1134028003
  return round(order + sign * seconds / 45000, 7)