Bronze Cowntact Tracing 2020 US Open Problem 3

Problems and Contests
#1

http://www.usaco.org/index.php?page=viewproblem2&cpid=1037

Hi everyone,

I was working on the problem above. I don’t understand how the the x value or the possible cows that can be patient zero is 1 in the sample case. I think x would be 2 because if K = 0, then 1 and 2 can both start infected and not spread the infection.

#2

(i) Exactly one cow on his farm could have started out carrying the disease (we’ll call this cow “patient zero”).

Exactly one cow.

#3

Oh so only one cow can start off infected. The minimum K would be 1, because cow 1 infects cow 2. Cow 1 is the only cow that can be patient zero because it needs to infect cow 2.

#4

Yes.