在std :: max_element上施加条件

Question

Is there any way to make std::max_element return the end iterator if no element is grater than a certain value?

Imagine I have this vector:

std::vector<int> vector{3, 6, 2, 5};
auto it = std::max_element(vector.begin(), vector.end());

How would you make it point to vector.end() if no element is greater than 7?

Answer 1

I don't see an algorithm to do this directly, but it's pretty trivial to tack it on after the fact:

auto temp = std::max_element(v.begin(), v.end());
auto it = (temp ==v.end() || *temp > 7) ? temp : v.end();

Answer 2

With range-v3 , you may do:

std::vector<int> v{3, 6, 2, 5};
auto r = v | ranges::view::filter([](auto e){ return e > 7; });
auto it = ranges::max_element(r);
if (it == r.end()) {
    std::cout << "End\n";
} else {
    std::cout << *it << std::endl;   
}

Demo