ranges_min_element.md

min_element

• algorithm[meta header]
• std::ranges[meta namespace]
• function template[meta id-type]
• cpp20[meta cpp]

namespace std::ranges {
  template <forward_iterator I,
            sentinel_for<I> S,
            class Proj = identity,
            indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>
  constexpr I
    min_element(I first,
                S last,
                Comp comp = {},
                Proj proj = {}); // (1) C++20

  template <forward_range R,
            class Proj = identity,
            indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less>
  constexpr borrowed_iterator_t<R>
    min_element(R&& r,
                Comp comp = {},
                Proj proj = {}); // (2) C++20
}

• forward_iterator[link /reference/iterator/forward_iterator.md]
• identity[link /reference/functional/identity.md]
• indirect_strict_weak_order[link /reference/iterator/indirect_strict_weak_order.md]
• projected[link /reference/iterator/projected.md]
• ranges::less[link /reference/functional/ranges_less.md]
• forward_range[link /reference/ranges/forward_range.md]
• iterator_t[link /reference/ranges/iterator_t.md]
• borrowed_iterator_t[link /reference/ranges/borrowed_iterator_t.md]

概要

[first, last)の範囲において、最小要素を指す最初のイテレータを取得する。

• (1): イテレータ範囲を指定する
• (2): Rangeを直接指定する

戻り値

比較 invoke(comp, invoke(proj, *i), invoke(proj, *j)) によって最小と判断された最初の要素を指すイテレータ

計算量

max((last - first) - 1, 0)回の比較を行う

例

#include <algorithm>
#include <cassert>
#include <utility>
#include <vector>

int main()
{
  std::vector<int> v1 = {3, 1, 4};

  auto v1_min_element = std::ranges::min_element(v1);
  assert(*v1_min_element == 1);


  std::vector<std::pair<int, int>> v2 = {{0, 3}, {1, 1}, {2, 4}};

  auto v2_min_element = std::ranges::min_element(v2, {}, &std::pair<int, int>::second);
  assert(v2_min_element->first == 1);
  assert(v2_min_element->second == 1);
}

• std::ranges::min_element[color ff0000]

出力

バージョン

言語

• C++20

処理系

• Clang: ??
• GCC: 10.1.0 [mark verified]
• ICC: ??
• Visual C++: 2019 Update 10 [mark verified]

参照

• N4861 25 Algorithms library