(*  S is a stream of items to sample, R will contain the result  S.Current returns current item in stream  S.Next advances stream to next position  max-priority-queue supports:    Count -> number of items in priority queue    Maximum -> returns maximum key value of all items    Extract-Max() -> Remove the item with max key    Insert(key, Item) -> Adds item with specified key *)ReservoirSample(S[1..?], R[1..k])  H = new max-priority-queue  while S has data    r = Random(0,1)    if H.Count < k      H.Insert(r, S.Current)    else      if H.Maximum > r        H.Extract-Max()        H.Insert(r, S.Current)    S.Next