NAME¶

std::ranges::minmax_element,std::ranges::minmax_element_result - std::ranges::minmax_element,std::ranges::minmax_element_result

Synopsis¶

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 (1) (since
= ranges::less > C++20)
constexpr minmax_element_result<I>

minmax_element( I first, S last, Comp comp = {}, Proj proj = {} );
template< ranges::forward_range R, class Proj = std::identity,

std::indirect_strict_weak_order<
std::projected<ranges::iterator_t<R>, Proj>> Comp = (2) (since
ranges::less > C++20)
constexpr minmax_element_result<ranges::borrowed_iterator_t<R>>

minmax_element( R&& r, Comp comp = {}, Proj proj = {} );

Helper types¶

template< class I > (3) (since
using minmax_element_result = ranges::min_max_result<I>; C++20)

1) Finds the smallest and largest elements 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 cannot be specified when calling any of them.
* None of them are visible to argument-dependent lookup.
* When any of them are found by normal unqualified lookup as the name to the left
of the function-call operator, argument-dependent lookup is inhibited.

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¶

An object consisting of an iterator to the smallest element as the first element and
an iterator to the greatest element as the second. Returns {first, first} if the
range is empty. If several elements are equivalent to the smallest element, the
iterator to the first such element is returned. If several elements are equivalent
to the largest element, the iterator to the last such element is returned.

Complexity¶

At most std::max(std::floor(1.5 * (N − 1)), 0.0) applications of the comparison and
twice as many applications of the projection, where N = ranges::distance(first,
last).

Possible implementation¶

struct minmax_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 ranges::minmax_element_result<I>
operator()(I first, S last, Comp comp = {}, Proj proj = {}) const
{
auto min = first, max = first;

if (first == last || ++first == last)
return {min, max};

if (std::invoke(comp, std::invoke(proj, *first),
std::invoke(proj, *min)))
min = first;
else
max = first;

while (++first != last)
{
auto i = first;
if (++first == last)
{
if (std::invoke(comp, std::invoke(proj, *i),
std::invoke(proj, *min)))
min = i;
else if (!(std::invoke(comp, std::invoke(proj, *i),
std::invoke(proj, *max))))
max = i;
break;
}
else
{
if (std::invoke(comp, std::invoke(proj, *first),
std::invoke(proj, *i)))
{
if (std::invoke(comp, std::invoke(proj, *first),
std::invoke(proj, *min)))
min = first;
if (!(std::invoke(comp, std::invoke(proj, *i),
std::invoke(proj, *max))))
max = i;
}
else
{
if (std::invoke(comp, std::invoke(proj, *i),
std::invoke(proj, *min)))
min = i;
if (!(std::invoke(comp, std::invoke(proj, *first),
std::invoke(proj, *max))))
max = first;
}
}
}
return {min, max};
}

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::minmax_element_result<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 minmax_element_fn minmax_element;

Example¶

// Run this code

#include <algorithm>
#include <iostream>
#include <iterator>
namespace ranges = std::ranges;

int main()
{
const auto v = {3, 9, 1, 4, 1, 2, 5, 9};
const auto [min, max] = ranges::minmax_element(v);
std::cout
<< "min = " << *min << ", at [" << ranges::distance(v.begin(), min) << "]\n"
<< "max = " << *max << ", at [" << ranges::distance(v.begin(), max) << "]\n";
}

Output:¶

min = 1, at [2]
max = 9, at [7]

See also¶

ranges::min_element returns the smallest element in a range
(C++20) (niebloid)
ranges::max_element returns the largest element in a range
(C++20) (niebloid)
ranges::minmax returns the smaller and larger of two elements
(C++20) (niebloid)
minmax_element returns the smallest and the largest elements in a range
(C++11) (function template)