# Exam WS 19/20 - Wrong Solutions?

Disclaimer: Dieser Thread wurde aus dem alten Forum importiert. Daher werden eventuell nicht alle Formatierungen richtig angezeigt. Der ursprüngliche Thread beginnt im zweiten Post dieses Threads.

Exam WS 19/20 - Wrong Solutions?
Not sure if someone mentioned this already, but I think there are two errors in the solution of the 19/20 Exam
(https://kwarc.info/teaching/AI/exams/WS1920/exam-with-solutions.pdf)

Problem 2.3 - Iterative Deepening

The solution in the PDF is:
A
A, B, C
A, B, D, E, C, F, G
A, B, D, E, H, J, C, F, G, I

I think there is one step missing, the correct solution should be:
A
A, B, C
A, B, D, E, C, F, G
A,B,D,E,H, C, F, G, I
A,B,D,E,H, J, C, F, G, I

Problem 5.2
And in 5.2, the solution “splits” up the formula wrong at the beginning, and ignores the first brackets.
It splits it up at the second =>, but it should split it at the third =>.

Correct me if I’m wrong!

Wrong Solutions Retake Exam 19/20
Retake Exam 19/20
Problem 5.2 First Order Tableuax:

Within the first step, there were substituted ForAllY and ForAllZ with ForAllX. I think this is an error within the solution or could this be a right solution somehow. If yes how do we get to this point?

Another mistake in notes?
Page 305

p ⊑ q c a n s t i l l b e u s e d a s a n a b b r e vi a t i o n f o r (Not)p ⊔ q

There is a second negation over the whole second term and I do not know where it comes from. Probably it is just a typing error?

Thanks for help!

Thanks.

Thanks. alpha-renaming is always allowed. Doing it is unusual and in this unnecessary but not allowed.

Alpha-Beta Pruning Retake WS19/20 (3.1.3)
Is the node “N” really pruned by alpha-beta? If this node is e.g. 6 the whole MinMax Value would go up to 6, so I assume this is an error in the solution?

1 Like

to capture your concern, i first thought the same but i think it is correct: sometimes implication A->B is written as A ⊃ B. Negated it would be A ⊆ B… but it’s just a guess, like in the world of numbers instead of sets, the relation > switches to <= if multiplying both sides by -1

EDIT: p ⊑ q <=> !(p ⊐ q) <=> !(!p ⊔ q)

I totally agree with you. H won’t return, because M ≱ beta with beta = 6 and M = 3. And thus N is not pruned

1 Like