Class that accepts iterator as argument, and stores values?

Suppose I want to implement a class that iterates over some range, and stores those values in an array at random indices. So I want something where I can write:

string s = "Steve";
auto r1 = RandomArray<string>(s.begin(), s.end());
// Or even better:
auto better1 = RandomArray(s);
int a[] = {1,2,3};
auto r2 = RandomArray<int>(begin(a), end(a));
// Or even better:
auto better2 = RandomArray(a);
// Later on...
for (const auto ch: r1) {/* do something */}

How would I define such a class? I can't figure out what the templating should look like. That is, how do I fill in what's missing below?

// template stuff
class RandomArray {
    public:
    RandomArray(/* some iterator argument(s) */) {
        // Pretend arr_ has already been sized correctly.
        for (const auto it = /* iterate over iterator */) {
            arr_[randomIndex()] = it;
        }
    }
    private:
    /* Some type */ arr_[];
};

I'm ignoring all the other things I'd eventually need (move constructors, begin/end, etc.). I just want to figure out what the template statement before the class should look like.