I believe this is a problem that CS has already solved: http://dimacs.rutgers.edu/~graham/pubs/papers/cmsoft.pdf

The Count-Min Sketch is a data structure consisting of a fixed array of counters.

This is a short and easily accessible paper, which isn't very heavy on math or obscure notation or concepts, so I would recommend it to anyone with even a cursory interest in the subject.

Here's an implementation in Python: https://github.com/barrust/count-min-sketch/blob/master/pyth...