Given an array nums, return [positives, negatives, zeros]: how many elements are greater than 0, less than 0, and exactly 0. Classifying a single number by its sign is a conditionals exercise; doing it for a whole array adds a loop and three counters. Zero is the case that is easiest to forget — it is neither positive nor negativeSign of ZeroZero is the boundary between positive and negative numbers and belongs to neither group. — and the second solution shows it does not even need its own branch.