Namespaces
Variants

    std::minmax_element

    From cppreference.com
     
    C++
     
    Algorithm library
    Constrained algorithms and algorithms on ranges (C++20)
    Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
    Non-modifying sequence operations    
    Batch operations
    (C++17)
    Search operations
    Modifying sequence operations
    Copy operations
    (C++11)
    (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
    (C++11)    
    (C++11)

    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
    (C++20)
    Permutation operations


     
    Defined in header <algorithm> 
    template< class ForwardIt >
std::pair<ForwardIt, ForwardIt>
    minmax_element( ForwardIt first, ForwardIt last );
    		(1) (since C++11)
    (constexpr since C++17)    		 
    template< class ForwardIt, class Compare >
std::pair<ForwardIt, ForwardIt>
    minmax_element( ForwardIt first, ForwardIt last, Compare comp );
    		(2) (since C++11)
    (constexpr since C++17)    		 
    template< class ExecutionPolicy, class ForwardIt >
std::pair<ForwardIt, ForwardIt>
    minmax_element( ExecutionPolicy&& policy,
                    ForwardIt first, ForwardIt last );
    		(3) (since C++17) 
    template< class ExecutionPolicy, class ForwardIt, class Compare >
std::pair<ForwardIt, ForwardIt>
    minmax_element( ExecutionPolicy&& policy,
                    ForwardIt first, ForwardIt last, Compare comp );
    		(4) (since C++17)
    See More

    Finds the smallest and greatest element in the target range [first, last).

    1) Elements are compared using operator<(until C++20)std::less{}(since C++20).
    2) Elements are compared using the comparison function comp.
    3,4) Same as (1,2), but executed according to policy.
    These overloads participate in overload resolution only if the value of the following expression is true:

    std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>

    		(until C++20)

    std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>

    		(since C++20)

    Parameters

    first, last - the pair of iterators defining the target range
    comp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if the first argument is less than the second.

    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 ForwardIt can be dereferenced and then implicitly converted to both of them.

    policy - the execution policy to use
    Type requirements
    -
    ForwardIt must meet the requirements of LegacyForwardIterator.

    Return value

    A std::pair object, where:

    • The data member first holds the iterator to the smallest element in the target range.
      • If there are multiple smallest values, first holds the iterator to the first one of them.
      • If the target range is empty, first holds last.
    • The data member second holds the iterator to the greatest element in the target range.
      • If there are multiple greatest values, second holds the iterator to the last one of them.
      • If the target range is empty, second holds last.

    Complexity

    Given N as std::distance(first, last):

    1) At most max(⌊
    3
    2
    (N-1)⌋,0)     comparisons using operator<(until C++20)std::less{}(since C++20).
    2) At most max(⌊
    3
    2
    (N-1)⌋,0)     applications of the comparator comp.
    3) 𝓞(N) comparisons using operator<(until C++20)std::less{}(since C++20).
    4) 𝓞(N) applications of the comparator comp.

    Exceptions

    3,4) During the execution process:
    • If the temporary memory resources required for parallelization are not available, std::bad_alloc is thrown.
    • If an uncaught exception is thrown while accessing objects via an algorithm argument, the behavior is determined by the execution policy (for standard policies, std::terminate is invoked).

    Notes

    This algorithm is different from std::make_pair(std::min_element(), std::max_element()), not only in efficiency, but also in that this algorithm finds the last biggest element while std::max_element finds the first biggest element.

    Possible implementation

    minmax_element (1) 
    template<class ForwardIt>
std::pair<ForwardIt, ForwardIt>
    minmax_element(ForwardIt first, ForwardIt last)
{
    using value_type = typename std::iterator_traits<ForwardIt>::value_type;
    return std::minmax_element(first, last, std::less<value_type>());
}
    minmax_element (2) 
    template<class ForwardIt, class Compare>
std::pair<ForwardIt, ForwardIt>
    minmax_element(ForwardIt first, ForwardIt last, Compare comp)
{
    auto min = first, max = first;
    
    if (first == last || ++first == last)
        return {min, max};
    
    if (comp(*first, *min))
        min = first;
    else
        max = first;
    
    while (++first != last)
    {
        auto i = first;
        if (++first == last)
        {
            if (comp(*i, *min))
                min = i;
            else if (!(comp(*i, *max)))
                max = i;
            break;
        }
        else
        {
            if (comp(*first, *i))
            {
                if (comp(*first, *min))
                    min = first;
                if (!(comp(*i, *max)))
                    max = i;
            }
            else
            {
                if (comp(*i, *min))
                    min = i;
                if (!(comp(*first, *max)))
                    max = first;
            }
        }
    }
    return {min, max};
}

    Example

    Run this code
    #include <algorithm>
#include <iostream>
 
int main()
{
    const auto v = {3, 9, 1, 4, 2, 5, 9};
    const auto [min, max] = std::minmax_element(begin(v), end(v));
    
    std::cout << "min = " << *min << ", max = " << *max << '\n';
}

    Output: 

    min = 1, max = 9

    See also

    (C++20)
    		 returns the smallest and the largest elements in a range
    (algorithm function object)[edit]
    		returns the smallest element in a range
    (function template & algorithm function object)[edit]
    (C++20)
    		returns the largest element in a range
    (function template & algorithm function object)[edit]
    (C++20)