collatz_seq.cpp

std::list<int> collatz_seq(int x)
{
    std::list<int> result;
    while (x > 1)
    {
        result.push_back(x);
        if (x % 2 == 0)
            x = x / 2;
        else
            x = 3 * x + 1;
    }
    result.push_back(x);
    return result;
}