C++ string class

If you have a C++ string and a char pointer

string str = "mudkipz";
char * ptr;

how would you iterate through each char in the string using only the pointer and only pointer notation? In other words, you can't assign the address with ptr = &str[0];

I don't see how it's possible, since a string isn't an array. If it were, I'd just do this

string str = "mudkipz";
    char * ptr = str;

    for(int i = 0; i < str.length(); ++i)
    {
        cout << *(ptr + i);
    }

Any ideas?

>>3
Ideas? It's part of a project for my course. And my professor doesn't seem like an idiot. Instead of contributing absolutely nothing, why don't you mention exactly what it is I'm doing that's so wrong? Stepping through a string with a char pointer? Please. Unless, of course, you don't really have any programming knowledge and just like to troll.