std::list remove element by index

Question

I have a std::list full of objects. Whenever I add a object, I want to store that objects index in the list, so later on I can remove it from the list.

What I want to do in pseudo code

myList.pushBack(element);
int index = myList.getIndexOfLastElement();

myList.erase(index);

For performance reasons I can't search by value.

To clarify: I have element a(index 0), b(index 1), c(index 2), d(index 3)

If I delete element b, I still want to be able to access c by 2.

Answer 1

I'd suggest using std::list::iterator instead of integer indices. std::list::erase() does not invalidate iterators.

auto index = myList.insert(myList.end(), element);

myList.erase(index);

Answer 2

You'll need to map the index s to the iterator for that element. Something like:

auto pos = myList.cbegin();
map<int, decltype(pos)> m;

// bump pos for every myList.pushBack(element);
int index = myList.getIndexOfLastElement();
m[index] = pos;

// then you can erase with
myList.erase(m[index]);