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× C++ Standard Library C++ STL Library


The C++ unordered_set::max_bucket_count function is used to return the maximum number of buckets that the unordered_set can have. It returns the maximum potential number of buckets the unordered_set can have due to known system or library implementation limitations.

As an unordered_set is implemented using hash table where a bucket is a slot in the container's internal hash table to which elements are assigned based on the hash value. The number of buckets directly influences the load_factor of the container's hash table. The container automatically increases the number of buckets to keep the load_factor below its max_load_factor which causes rehash whenever the number of buckets is increased.

Syntax

size_type max_bucket_count() const noexcept;

Parameters

No parameter is required.

Return Value

The maximum number of buckets in the unordered_set.

Time Complexity

Constant i.e, Θ(1).

Example:

In the below example, the unordered_set::max_bucket_count function is used to find out the maximum number of buckets that the unordered_set can have.

#include <iostream>
#include <unordered_set>
using namespace std;
 
int main (){
  unordered_set<int> uSet;

  cout<<"Max size = "<<uSet.max_size()<<"\n";
  cout<<"Max bucket count = "<<uSet.max_bucket_count()<<"\n";
  cout<<"Max load factor = "<<uSet.max_load_factor()<<"\n";

  return 0;
}

A possible output could be:

Max size = 1152921504606846975
Max bucket count = 1152921504606846975
Max load factor = 1

❮ C++ <unordered_set> Library