Defined in header <set> template<
class Key,
class Compare = std::less<Key>,
class Allocator = std::allocator<Key>
> class multiset;
Multiset is an associative container that contains a sorted set of objects of type Key. Unlike set, multiple keys with equivalent values are allowed. Sorting is done using the key comparison function Compare. Search, insertion, and removal operations have logarithmic complexity.
Everywhere the standard library use