2. リファレンス
3. unordered_set
4. unordered_multiset
5. load_factor

最終更新日時: 2026年09月11日 13時06分31秒 (JST)
Akira Takahashi が更新

履歴 編集

std::unordered_multiset::load_factor(C++11)

float load_factor() const noexcept;           // (1) C++11
constexpr float load_factor() const noexcept; // (1) C++26

size() / bucket_count()

#include <iostream>
#include <unordered_set>
#include <algorithm>
#include <iterator>

template <class C>
void print(const C& c, std::ostream& os = std::cout)
{
  std::copy(c.begin(), c.end(), std::ostream_iterator<typename C::value_type>(os, ", "));
  os << "\nsize is " << c.size() << ", bucket_count is " << c.bucket_count() << ", load_factor is " << c.load_factor() << '\n' << std::endl;
}

int main()
{
  std::unordered_multiset<int> ums{ 1, 3, 5, 7, 9, 1, 3, 5, 7, 9, };

  print(ums);

  ums.insert({ 2, 4, 6, 8, 10, 2, 4, 6, 8, 10, });

  print(ums);
}

9, 9, 7, 7, 5, 5, 1, 1, 3, 3,
size is 10, bucket_count is 11, load_factor is 0.909091

10, 10, 8, 8, 6, 6, 4, 4, 2, 2, 9, 9, 7, 7, 5, 5, 1, 1, 3, 3,
size is 20, bucket_count is 23, load_factor is 0.869565