How to find the length of a string without .length()?

[awong918]

string x = "hello"

How would I be able to find the length of this string w/o using x.length()?

[JLBorges]

x.size() or
x.end() - x.begin() or
x.rend() - x.rbegin()
etc.

but not, std::strlen( x.c_str() )