Do I have a misunderstanding of loop invarients?

Asked Sep 21 '22 at 22:44

Active Sep 21 '22 at 22:44

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So I have an upcoming test about proofs and I was looking through some practice questions. I came across a question which I don't understand the answer to, and I was hoping I could get some input.

Consider the following algorithm:
Factorial(n: integer > 0)
temp = 1
for i = 1 to n do
        temp = temp * i
return temp
Write down the loop invariant for the loop in this algorithm.

The answer marked as correct is:

before loop, temp = i = 1

Why is this correct? I'm struggling to understand how it proves the validity of the algorithm. Here is what I would have put, which I am also uncertain about:

before each loop, temp = (i - 1)!

Thanks in advance.

asked Sep 21 '22 at 22:44

Harper Rhett

This question might help: https://stackoverflow.com/questions/17008219/how-to-find-loop-invariant-java – Don Branson Sep 21 '22 at 22:49
I like your invariant, it makes more sense to me. – President James K. Polk Sep 21 '22 at 23:00
As you put it the answer that was given is indeed not the loop invariant... But it might be good to literally quote the whole context, and possibly link to it as well. – trincot Sep 22 '22 at 05:50

Do I have a misunderstanding of loop invarients?

0 Answers0