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Showing content from https://en.cppreference.com/w/cpp/language/../error/error_code/../../error/../algorithm/minmax.html below:

std::minmax - cppreference.com

Returns the lowest and the greatest of the given values.

1,2) Returns references to the smaller and the greater of a and b.

1) Uses operator< to compare the values.

2) Use the comparison function comp to compare the values.

3,4) Returns the smallest and the greatest of the values in initializer list ilist.

3) Uses operator< to compare the values.

4) Use the comparison function comp to compare the values.

The signature of the comparison function should be equivalent to the following:

bool cmp(const Type1& a, const Type2& b);

While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type T can be implicitly converted to both of them.

Returns the result of

if

or if

is equivalent to

. Returns the result of

if

.

3,4) A pair with the smallest value in ilist as the first element and the greatest as the second. If several elements are equivalent to the smallest, the leftmost such element is returned. If several elements are equivalent to the largest, the rightmost such element is returned.

1) Exactly one comparison using operator<.

2) Exactly one application of the comparison function comp.

3,4) Given \(\scriptsize N\)N as ilist.size():

At most

comparisons using

.

At most

applications of the comparison function

.

template<class T>
constexpr std::pair<const T&, const T&> minmax(const T& a, const T& b)
{
    return (b < a) ? std::pair<const T&, const T&>(b, a)
                   : std::pair<const T&, const T&>(a, b);
}

template<class T, class Compare>
constexpr std::pair<const T&, const T&> minmax(const T& a, const T& b, Compare comp)
{
    return comp(b, a) ? std::pair<const T&, const T&>(b, a)
                      : std::pair<const T&, const T&>(a, b);
}

template<class T>
constexpr std::pair<T, T> minmax(std::initializer_list<T> ilist)
{
    auto p = std::minmax_element(ilist.begin(), ilist.end());
    return std::pair(*p.first, *p.second);
}

template<class T, class Compare>
constexpr std::pair<T, T> minmax(std::initializer_list<T> ilist, Compare comp)
{
    auto p = std::minmax_element(ilist.begin(), ilist.end(), comp);
    return std::pair(*p.first, *p.second);
}

For overloads (1,2), if one of the parameters is a temporary, the reference returned becomes a dangling reference at the end of the full expression that contains the call to minmax:

int n = 1;
auto p = std::minmax(n, n + 1);
int m = p.first; // ok
int x = p.second; // undefined behavior
 
// Note that structured bindings have the same issue
auto [mm, xx] = std::minmax(n, n + 1);
xx; // undefined behavior

#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v{3, 1, 4, 1, 5, 9, 2, 6};
    std::srand(std::time(0));
    std::pair<int, int> bounds = std::minmax(std::rand() % v.size(),
                                             std::rand() % v.size());
 
    std::cout << "v[" << bounds.first << "," << bounds.second << "]: ";
    for (int i = bounds.first; i < bounds.second; ++i)
        std::cout << v[i] << ' ';
    std::cout << '\n';
}

Possible output:

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

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