loop problem

[EwCjE3v7]

Why does the following loop never exit?

vector<int> vi = {1,2,3,4,5,6,7,8,9};
	auto iter = vi.begin();

	while (iter != vi.end()) {
		if (*iter % 2) {
			iter = vi.insert(iter, *iter);
		}
		++iter;
	}

[AbstractionAnon]

Because you're forever adding entries to the vector.

When you get to any odd number, you add it to the end of the vector, thereby increasing the size of the vector.

edit: Struck out "the end of".

[MiiNiPaa]

Note that insert() returns iterator to the returned element.
What happens on vector {2, 4, 5, 6}
1) Iteration goes until first odd number:

2, 4, 5, 6
//    ↑iterator 

2) then you insert this value again:

2, 4, 5, 5, 6
//    ↑iterator to the fresly inserted value 

3) then you increment iterator

2, 4, 5, 5, 6
//       ↑iterator 

4) Value is odd again, goto (2)

[EwCjE3v7]

Oh thank you all, so I would need to do iter += 2; to fix it. Thank you guys