The max_size() of unordered_multiset takes the maximum number of elements that the unordered_multiset container is able to hold due to system or It gets the maximum size of the controlled sequence.
size_type max_size() const;
where size_type is an unsigned integral type.
Returns : The member function returns the length of the longest sequence that the object can hold. In short, the maximum number of elements.
Below program illustrate the unordered_multiset max_size function :-
Maximum size = 1152921504606846975 Current size = 6
It takes constant(O(1)) time of complexity to perform an operation.