Might not be very obscure but it was new to me. Ended up being really useful for finding out whether dates intersect a particular period and ended up using it quite a bit at work.
You give it a range of dates and it'll tell you if any intersect so if you're looking for "how many people are absent in this time period" you can really quickly find out by using a range tree.
Range Tree:
https://en.wikipedia.org/wiki/Range_tree
You give it a range of dates and it'll tell you if any intersect so if you're looking for "how many people are absent in this time period" you can really quickly find out by using a range tree.