Finds the last position of one of the elements in the function's argument starting from the beginning.
size_type find_last_of (const basic_string& str,size_type pos = npos) const; size_type find_last_of (const charT* s, size_type pos, size_type n) const; size_type find_last_of (const charT* s, size_type pos = npos) const; size_type find_last_of (charT c, size_type pos = npos) const;
The found position or npos if not found is returned.