I'm new to functors theme, so I hope this question will be constructive.

I have array of strings (). I need to calculate the sum of lenghts of these strings with help of functors.

My code:

```
class LengthFinder{
    private:
        size_t sum;
    public:
        LengthFinder():sum(0){}

    void operator()(string elem)
    {
        sum += elem.size();
    }
    operator int()
    {
        return sum;
    }

};

int main(int argc, char* argv[])
{
    vector< string > array;
    array.push_back("string");
    array.push_back("string1");
    array.push_back("string11");

    string elem;
    int sum = std::for_each(array.begin(), array.end(), LengthFinder(/*??*/));
    return 0;
}

```

What should I pass to LengthFinder(), to get each string and take it size?