Random Shuffles
Shuffling a collection of items is a surprisingly frequent task in programming: essentially, it comes up whenever a known input must be processed in random order. What is more, there is a delightful, three-line algorithm to accomplish this task correctly, in-place, and in optimal time. Unfortunately, this simple three-line solution seems to be insufficiently known, leading to various, less-than-optimal ad-hoc alternatives being used in practice — but that is entirely unnecessary!