The OP should have mentioned that it's this algorithm: https://en.wikipedia.org/wiki/Reservoir_sampling https://en.wikipedia.org/wiki/Reservoir_sampling IMO i

The OP should have mentioned that it's this algorithm: https://en.wikipedia.org/wiki/Reservoir_sampling https://en.wikipedia.org/wiki/Reservoir_sampling IMO it's a lot clearer if it's not in Perl ... The pseudocode in Wikipedia also avoids division.