std::max_element

Since C++17

Header: <algorithm>

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

# Declarations

template< class ForwardIt >
ForwardIt max_element( ForwardIt first, ForwardIt last );

(constexpr since C++17)

template< class ExecutionPolicy, class ForwardIt >
ForwardIt max_element( ExecutionPolicy&& policy,
ForwardIt first, ForwardIt last );

(since C++17)

template< class ForwardIt, class Compare >
ForwardIt max_element( ForwardIt first, ForwardIt last,
Compare comp );

(constexpr since C++17)

template< class ExecutionPolicy, class ForwardIt, class Compare >
ForwardIt max_element( ExecutionPolicy&& policy,
ForwardIt first, ForwardIt last,
Compare comp );

(since C++17)

# Parameters

first, last: forward iterators defining the range to examine
policy: the execution policy to use
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.

# 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.

# 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';
}

# Defect reports

DR	Applied to	Behavior as published	Correct behavior
LWG 212	C++98	the return value was not specified if [first, last) is empty	returns last in this case
LWG 2150	C++98	the iterator to the first non-smallest element was returned	corrected the return value