Insert into this unordered multiset a newly created value_type object, constructed by forwarding get_allocator() (if required) and the specified (variable number of) args to the corresponding constructor of value_type (in constant time if the specified hint refers to an element in this container equivalent to the newly created value_type object). Return an iterator referring to the newly created and inserted object in this unordered multiset whose value is equivalent to that of an object constructed from args. If hint does not refer to an element in this container equivalent to the newly created value_type object, this operation has worst case O[N] and average case constant-time complexity, where N is the size of this unordered multiset. This method requires that the (template parameter) type KEY be emplace-constructible into this unordered multiset from args (see {Requirements on KEY}). The behavior is undefined unless hint is an iterator in the range [begin() .. end()] (both endpoints included).
Declared in <bslstl_unorderedmultiset.h>
template<class... Args>
unordered_multiset<KEY, HASH, EQUAL, ALLOCATOR>::iterator
emplace_hint(
const_iterator hint,
Args&&... args);