I don’t understand the point of this article. There is no requirement stated regarding the properties of the ordering - in fact there is no code at all that depends on the traversing the map elements in a particular order. So you can pick any ordering you want.
If the requirement is “use std::map to store items but prevent adding items to the map if they have a particular relationship to existing map keys”, then this is a terrible solution - std::map like maps and dictionaries in all programming language is not designed for this - it should never be an error to add a value associated with a key to a map instance. Hacking the ordering to implement a requirement like this is brittle, obscure and strange.
If this were proposed as a solution to the problem “design a data structure to store values keyed by intervals that prevents overlapping intervals”, then I would mark it very low.
If the requirement is “use std::map to store items but prevent adding items to the map if they have a particular relationship to existing map keys”, then this is a terrible solution - std::map like maps and dictionaries in all programming language is not designed for this - it should never be an error to add a value associated with a key to a map instance. Hacking the ordering to implement a requirement like this is brittle, obscure and strange.
If this were proposed as a solution to the problem “design a data structure to store values keyed by intervals that prevents overlapping intervals”, then I would mark it very low.