std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>:: ~unordered_multimap

From cppreference.com

~unordered_multimap ( ) ;
(since C++11)

A destructor . Destructs the unordered_multimap . The destructors of the elements are called and the used storage is deallocated. Note, that if the elements are pointers, the pointed-to objects are not destroyed.

Complexity

Linear in the size of the unordered_multimap .