How to erase from vector by iterator?

Question

I want to erase elements by indexes. Inside eraseIndexs function I access to begin & end iterators.When I create a vector from begin and end iterators create a new vector from them.

How to erase elements by iterators?

template <typename ForwardIt>
void eraseIndexs(ForwardIt& begin, ForwardIt& end, const vector<size_t>& indexs){
    using T = typename iterator_traits<ForwardIt>::value_type;
    vector<T> v(begin, end);
    for (size_t index = 0; index < indexs.size(); index++)
        v.erase(v.begin() + indexs[index] - index);
}

Duplicate: http://stackoverflow.com/questions/23122555/removing-by-index-from-a-c-vector-using-remove-if — D Drmmr, Jun 21 '14 at 18:31
"I want to erase elements by indexes." followed by "How to erase elements by iterators?" What do you want actually? — Borgleader, Jun 21 '14 at 18:31
I have no idea what you're trying to do. why do you try to manipulate a local variable (vector) that will fall out of scope? — Karoly Horvath, Jun 21 '14 at 18:38
@KarolyHorvath I think we can assume it won't. It's good that people provide SSCCE's :) — keyser, Jun 21 '14 at 19:00
@LightnessRacesinOrbit I know. I mean in the _real_ code. I'm assuming there is such a thing since the above code does nothing. — keyser, Jun 21 '14 at 19:42

score 2 · Accepted Answer · answered Jun 21 '14 at 20:25

You are not erasing anything

you are making a local std:vector in your function :

vector<T> v(begin, end);

and then erasing from it

v.erase(v.begin() + indexs[index] - index);

It doesn't erase your real vector's iterator .

If you want to erase from vector :

you have to pass std::vector to your function and use erase member function :

template <typename Container>
void eraseIndexs(Container& c, const vector<size_t>& indexs){
    for (size_t index = 0; index < indexs.size(); index++)
        c.erase(c.begin() + indexs[index] - index);
}

How to erase from vector by iterator?

1 Answers1