Question

std::map should be implemented with a binary search tree as I read in the documentation and it sorts them too.

I need to insert rapidly and retrieve rapidly elements. I also need to get the first lowest N elements from time to time.

I was thinking about using a std::map, is it a good choice? If it is, what is the time I would need to retrieve the lowest N elements? O(n*logn)?

Answer 1

Given you need both retrieval and n smallest, I would say std::map is reasonable choice. But depending on the exact access pattern std::vector with sorting might be a good choice too.

I am not sure what you mean by retrieve. Time to read k elements is O(k) (provided you do it sequentially using iterator), time to remove them is O(k log n) (n is the total amount of elements; even if you do it sequentially using iterators).