sizeof() a vector

c++, sizeof, vector

Solution

You want `vector::size()` and `set::size()`.

Assuming `v` is your vector, do this:

size_t size = 0;
for (vector<set<char> >::const_iterator cit = v.begin(); cit != v.end(); ++cit) {
    size += cit->size();
}

`sizeof()` is giving you the in-memory size of the object/type it is applied to, in multiples of `sizeof(char)` (usually one byte). If you want to know the in-memory size of the container and its elements, you could do this:

`sizeof(v) + sizeof(T) * v.capacity(); // where T is the element type`

Problem

I have a `vector<set<char> >` data structure (transactions database) and I want to know the size of it. When I use sizeof() with each `set<char>` the size is 24 in spite of the set contains 3, 4 or 5 chars. Later, when I use sizeof() with the `vector<set<char> >` the size is 12... I suppose this is not the way to know the size of a data structure. Any help? Thanks.

Original source