The underlying reasoning behind PCSA/HLL (that if you squint, you can use the zeros and ones from a hash as analogues to coin-flipping, and can use the probabil

The underlying reasoning behind PCSA/HLL (that if you squint, you can use the zeros and ones from a hash as analogues to coin-flipping, and can use the probability of the rarest event seen to estimate the total number of events seen) is excellent. Count-min-sketch is also beautifully simple.