C++ Standard Library C++ STL Library

C++ unordered_multiset - max_size() Function

The C++ unordered_multiset::max_size function returns the maximum size the unordered_multiset can reach. The function returns the maximum potential size the unordered_multiset can reach due to known system or library implementation limitations.


size_type max_size() const noexcept;


No parameter is required.

Return Value

Maximum number of elements that can be held in a unordered_multiset.

Time Complexity

Constant i.e, Θ(1).


In the example below, the unordered_multiset::max_size function is used find out the maximum number of elements that a unordered_multiset can hold.

#include <iostream>
#include <unordered_set>
using namespace std;
int main (){
  unordered_multiset<int> uMSet{55, 25, 128, 5, 72};
  unordered_multiset<int>::iterator it;

  cout<<"The Unordered Multiset contains:";
  for(it = uMSet.begin(); it != uMSet.end(); ++it)
    cout<<" "<<*it;

  cout<<"\nUnordered Multiset size is: "<<uMSet.size()<<"\n";
  cout<<"Maximum size of the Unordered Multiset: "<<uMSet.max_size()<<"\n"; 
  return 0;

A possible output could be:

The Unordered Multiset contains: 72 128 5 25 55
Unordered Multiset size is: 5
Maximum size of the Unordered Multiset: 576460752303423487

❮ C++ <unordered_set> Library