std:: max_element

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

Parameters

Return value

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

Complexity

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

Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies , std::terminate is called. For any other ExecutionPolicy , the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

template<class ForwardIt>
ForwardIt max_element(ForwardIt first, ForwardIt last)
{
    if (first == last)
        return last;
 
    ForwardIt largest = first;
 
    while (++first != last)
        if (*largest < *first)
            largest = first;
 
    return largest;
}

template<class ForwardIt, class Compare>
ForwardIt max_element(ForwardIt first, ForwardIt last, Compare comp)
{
    if (first == last)
        return last;
 
    ForwardIt largest = first;
 
    while(++first != last)
        if (comp(*largest, *first))
            largest = first;
 
    return largest;
}

Example

#include <algorithm>
#include <cmath>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v{3, 1, -14, 1, 5, 9, -14, 9};
    std::vector<int>::iterator result;
 
    result = std::max_element(v.begin(), v.end());
    std::cout << "Max element found at index "
              << std::distance(v.begin(), result)
              << " has value " << *result << '\n';
 
    result = std::max_element(v.begin(), v.end(), [](int a, int b)
    {
        return std::abs(a) < std::abs(b);
    });
    std::cout << "Absolute max element found at index "
              << std::distance(v.begin(), result)
              << " has value " << *result << '\n';
}

Max element found at index 5 has value 9
Absolute max element found at index 2 has value -14

Defect reports

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

See also