Computer Science Canada

Round 3 Question 5 Sample Case?

Author:  xthexder [ Tue Jan 10, 2012 8:15 pm ]
Post subject:  Round 3 Question 5 Sample Case?

I didn't participate in this round, but going over the questions after, I noticed this in the sample test case:

((a ^ b) v (c ^ ~c)) is supposedly a tautology?
I'm confused because as I see it, it is not a tautology, but no-one else seems to have said anything.
What am I missing?

((a ^ b) v (c ^ ~c))
= ((a and b) or (c and ~c))
= ((a and b) or (false))
= (a and b)

if a or b == false, then it's false.

Don't tell me c is some tri-state variable...


Author:  Tony [ Tue Jan 10, 2012 9:42 pm ]
Post subject:  RE:Round 3 Question 5 Sample Case?

We actually caught that mistake during the contest; there was a notice put up. The sample was supposed to read

((a ^ b) v ~(c ^ ~c))

Not sure why the archived version of the sample is reverted to the wrong copy...