std::ranges::min_element

Defined in header `<algorithm>`
Call signature
template< std::forward_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_strict_weak_order<std::projected<I, Proj>> Comp = ranges::less > constexpr I min_element( I first, S last, Comp comp = {}, Proj proj = {} );	(1)	(since C++20)
template< ranges::forward_range R, class Proj = std::identity, std::indirect_strict_weak_order< std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less > constexpr ranges::borrowed_iterator_t<R> min_element( R&& r, Comp comp = {}, Proj proj = {} );	(2)	(since C++20)

1) Finds the smallest element in the range [first, last).

2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.

The function-like entities described on this page are niebloids, that is:

Explicit template argument lists may not be specified when calling any of them.
None of them is visible to argument-dependent lookup.
When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.

In practice, they may be implemented as function objects, or with special compiler extensions.

Parameters

first, last	-	iterator-sentinel pair denoting the range to examine
r	-	the range to examine
comp	-	comparison to apply to the projected elements
proj	-	projection to apply to the elements

Return value

Iterator to the smallest element in the range [first, last). If several elements in the range are equivalent to the smallest element, returns the iterator to the first such element. Returns first if the range is empty.

Complexity

Exactly $max(N-1,0)$ comparisons, where N = ranges::distance(first, last).

Possible implementation

struct min_element_fn {
  template<std::forward_iterator I, std::sentinel_for<I> S, class Proj = std::identity,
           std::indirect_strict_weak_order<std::projected<I, Proj>> Comp = ranges::less>
  constexpr I operator()(I first, S last, Comp comp = {}, Proj proj = {}) const
  {
    if (first == last) {
      return last;
    }
 
    auto smallest = first;
    ++first;
    for (; first != last; ++first) {
        if (!std::invoke(comp, std::invoke(proj, *smallest), std::invoke(proj, *first))) {
            smallest = first;
        }
    }
    return smallest;
  }
 
  template<ranges::forward_range R, class Proj = std::identity,
           std::indirect_strict_weak_order<
               std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less>
  constexpr ranges::borrowed_iterator_t<R>
  operator()(R&& r, Comp comp = {}, Proj proj = {}) const
  {
    return (*this)(ranges::begin(r), ranges::end(r), std::ref(comp), std::ref(proj));
  }
};
 
inline constexpr min_element_fn min_element;

Example

Run this code

#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>
 
int main()
{
    std::vector<int> v{ 3, 1, -14, 1, 5, 9 };
 
    namespace ranges = std::ranges;
    auto result = ranges::min_element(v.begin(), v.end());
    std::cout << "min element at: " << ranges::distance(v.begin(), result) << '\n';
 
    auto abs_compare = [](int a, int b) { return (std::abs(a) < std::abs(b)); };
    result = ranges::min_element(v, abs_compare);
    std::cout << "min element (absolute) at: " << ranges::distance(v.begin(), result) << '\n';
}

Output:

min element at: 2
min element (absolute) at: 1

Compiler support
Freestanding and hosted
Language
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Technical specifications
Symbols index
External libraries

ranges::max_element (C++20)	returns the largest element in a range (niebloid)
ranges::minmax_element (C++20)	returns the smallest and the largest elements in a range (niebloid)
ranges::max (C++20)	returns the greater of the given values (niebloid)
min_element	returns the smallest element in a range (function template)