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From: chrisj@basser.oz (Christopher Jack)
Newsgroups: sci.math
Subject: angels and devils
Message-ID: <806@basser.oz>
Date: Mon, 10-Nov-86 18:18:33 EST
Article-I.D.: basser.806
Posted: Mon Nov 10 18:18:33 1986
Date-Received: Tue, 11-Nov-86 07:51:10 EST
Organization: Dept of Comp Sci, Uni of Sydney, Australia
Lines: 21
Keywords: answer for simple case

If the angel is allowed to move only one planet, there is a very
simple algorithm that assures that the devil will win.

Outline (to give the idea)

First destroy the planet immediately above the angel

If the angel moves down, destroy the planet immediately below the angel
else If the angel moves sideways, destroy the planet diagonally up from the angel
	{if the angel moves down, destroy the planet underneath it
	 else if the angel moves up, destroy the planet above it
	 else (sideways), the next planet in the same direction}

Repeat the algorithm (approx) until angel is trapped

Basically the algorithm prevents the angel moving more than a certain
distance in any direction, and eventually traps.

I've left out a lot of fiddly bits but I think the idea is correct

chrisj@basser.OZ