Remove elements in a vector

In C++17

C++

auto p = std::remove_if(
    std::begin(a), std::end(a), [](const auto& e) { return e.seleted(); });
a.erase(p, std::end(a))

The complexity is $O(n)$

In C++20, we can do

c++

auto p = ranges::remove_if(a, &E::selected);
a.erase(p, std::end(a))