comments about Q2 a)


In the answers, most of students didn't show a clear proving structure.


What is the assumption,


Why w can be chosen as 0^n1^2n


and how to lead to a contradiction.


If the whole idea of prove is clear, I usually ignore the missing points
such as assume for all, exist etc.


If without clear reason, only assume y=0^i, 2 to 3 points deducted.


If no clear explanation why xz or xyyz is not in the language, 2 points
deducted.



comments about Q4


For a correct prove



reflexive: 3 points


symmetric: 3 points


transitive: 4 points


If there is no clear proving but mentioned 3 conditions to be an
equivalence conditions. 2 points are awarded.


Many people don't understand what does it means to be equivalent class and
prove something by induction. they got 0 points.


Question 5:


Most of people did the question very well.


4 points for correct answer


6 points for the process to prove the minimal DFA.


A few guys works out wrong answer and get no points.