your class should really have a single member variable, which is 'word'. The member "length" is not needed since it can be deduced by word, and represents a duplication of information (which, in general, is a bad thing). The variables 'result' and 'buffer' should be local to the function which uses them, since they make no sense outside that function.
as already said, you should stick with the names provided in the assignment.
Possible rewriting: