16 secret agents in Geneva
Source: Switzerland - Swiss TST 2001 p9
February 18, 2020
combinatorics
Problem Statement
In Geneva there are secret agents, each of whom is watching one or more other agents. It is known that if agent is watching agent , then is not watching . Moreover, any agents can be ordered so that the first is watching the second, the second is watching the third, etc, the last is watching the first. Show that any agents can also be so ordered.