Question

I want to use a structure in which I insert integers, and then can ask

if (container.contains(3)) { /**/ }

There has to be something like this.

Answer 1

You can use std::vector.

std::vector<int> myVec;
myVec.push_back(3);
if (std::find(myVec.begin(), myVec.end(), 3) != myVec.end())
{
    // do your stuff
}

You can even make a little helper function:

template <class T>
bool contains(const std::vector<T> &vec, const T &value)
{
    return std::find(vec.begin(), vec.end(), value) != vec.end();
}

Here is how you would use it:

if (contains(myVec, 3)) { /*...*/ }