[OT] Retreating from Iraq

[Andrei Alexandrescu]

Suppose that a miracle happen and the decision is taken at the highest 
level to retreat all of US military presence from Iraq. That will take a 
while, but sending the orders quickly is a must.

For utmost certainty, all orders are to be sent via phone and down the 
command chain, and only to direct subordinates. Each officer has a 
variable number of subordinates. Initially the president calls his 
immediate subordinates, who call their immediate subordinates, etc. Each 
call can be assumed to take the same amount of time.

Devise an algorithm that ensures every foot soldier gets the news as 
quickly as possible, show it is correct, and show it is fast.


Andrei