Jul 13, 2015
#45 Robot Uprising
121 computers arranged in an 11 x 11 grid have gone rogue!
Fortunately, any individual computer can be cured and made "friendly" again.
Furthermore, if a rogue computer is neighbouring two friendly computers then it will be persuaded to become friendly too. ("Neighbouring" = "sharing an edge".)
How many computers must individually be cured to return the entire network friendly again?
Can you prove a lower bound?
(Click the picture to play.)