c++ - Modifying a data structure while iterating over it

Question

What happens when you add elements to a data structure such as a vector while iterating over it. Can I not do this?

I tried this and it breaks:

int main() {
    vector<int> x = { 1, 2, 3 };

    int j = 0;
    for (auto it = x.begin(); it != x.end(); ++it) {
        x.push_back(j);
        j++;
        cout << j << " .. ";
    }
}

Answer 1

Iterators are invalidated by some operations that modify a std::vector.

Other containers have various rules about when iterators are and are not invalidated. This is a post (by yours truly) with details.

By the way, the entrypoint function main() MUST return int:

int main() { ... }