Question

Is it allowed to erase an element pointed by iterator, and advance the same iterator in one line to go to next element?

set<int>::iterator it = S.begin();
while (it != S.end()) {
    if (shouldBeRemoved(*it)) {
        S.erase(it++); // is this line valid?
    } else {
        ++it;
    }
}

Answer 1

Is it allowed to erase an element pointed by iterator, and advance the same iterator in one line to go to next element?

Yes, it is valid.

---

Rationale:

it++ increments it so that it refers to the next element but yields a copy of its
original value. Thus, it doesn’t refer to the element that is removed when erase() is called.
And in case of std::set only iterators to the erased element are invalidated.^#1

You can consider this code example as a boilerplate code to remove an element to which your iterator is referring.

---

References:

For std::set,
^#1C++03 Standard 23.1.2/8:

Only iterators and references to the erased elements are invalidated