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std::ranges::min_element

From cppreference.com
< cpp‎ | algorithm‎ | ranges
 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
Constrained algorithms
Non-modifying sequence operations
Modifying sequence operations
Partitioning operations
Sorting operations
Binary search operations (on sorted ranges)
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
ranges::min_element
Permutation operations
Numeric operations
Fold operations
Operations on uninitialized storage
Return types
 
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 [firstlast).
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:

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

Contents

[edit] 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

[edit] Return value

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

[edit] Complexity

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

[edit] 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;
        while (++first != last)
            if (std::invoke(comp, std::invoke(proj, *first), std::invoke(proj, *smallest)))
                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;

[edit] Example

#include <algorithm>
#include <array>
#include <cmath>
#include <iostream>
 
int main()
{
    namespace ranges = std::ranges;
 
    std::array v{3, 1, -13, 1, 3, 7, -13};
 
    auto iterator = ranges::min_element(v.begin(), v.end());
    auto position = ranges::distance(v.begin(), iterator);
    std::cout << "min element is v[" << position << "] == " << *iterator << '\n';
 
    auto abs_compare = [](int a, int b) { return (std::abs(a) < std::abs(b)); };
    iterator = ranges::min_element(v, abs_compare);
    position = ranges::distance(v.begin(), iterator);
    std::cout << "|min| element is v[" << position << "] == " << *iterator << '\n';
}

Output:

min element is v[2] == -13
|min| element is v[1] == 1

[edit] See also

returns the largest element in a range
(niebloid)[edit]
returns the smallest and the largest elements in a range
(niebloid)[edit]
returns the greater of the given values
(niebloid)[edit]
returns the smallest element in a range
(function template) [edit]