I'm in search of an associative container that does not need an implementation of operator< for the key type. std::map and std::set requires that, so I think that I need another kind of associative container.
I can always implement my own contained using a vector of pairs, but I will lose the O(1) access of a key-value pair.
So what's the big deal about writing that operator overload ? I'm guessing those containers need that operator so that they can make binary searches. If the data is not ordered then they would have to resort to simple sequential linear searches.