Three implementations of Hoare's Quicksort

HN commenters point to it as programming inspiration and as a source of Bentley's anecdotes about adding function by deleting code.

Jon Bentley walks through three implementations of Hoare's Quicksort, from a dozen-line C function to a series of systematic code transformations that make the program ever simpler and more powerful. It is a Google Tech Talk on code elegance and program derivation.