B Trees. You can call them a set of algorithms or a data structure if you prefer, but its core idea can be expressed as an algorithm: making the root of the tre

B Trees. You can call them a set of algorithms or a data structure if you prefer, but its core idea can be expressed as an algorithm: making the root of the tree emerge from leaves. It's kind of democratic! Edit: it's also a massively practic idea that powers most databases.