Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!nike!ucbcad!ucbvax!jade!eris!mwm From: mwm@eris.BERKELEY.EDU (Mike (Don't have strength to leave) Meyer) Newsgroups: sci.math Subject: Re: angels and devils Message-ID: <1527@jade.BERKELEY.EDU> Date: Mon, 27-Oct-86 02:13:22 EST Article-I.D.: jade.1527 Posted: Mon Oct 27 02:13:22 1986 Date-Received: Mon, 27-Oct-86 22:11:52 EST References: <2056@princeton.UUCP> <514@aurora.UUCP> <126@fortune.UUCP> Sender: usenet@jade.BERKELEY.EDU Reply-To: mwm@eris.BERKELEY.EDU (Mike (Don't have strength to leave) Meyer) Organization: Missionaria Phonibalonica Lines: 29 In article <126@fortune.UUCP> stirling@fortune.UUCP (Patrick stirling) writes: >As a reminder, the problem is: >Planets arranged at the grid points on an infinite plane. An angel >is on a planet, and can travel up to 100 planets' distance in a day. >There is a devil who can destroy one planet anywhere each day. Can >the devil trap the angel? Thank you. I'd missed the original problem. But you've got an ambiguity: Can the angel teleport, or does it have to traverse the intervening planets? If the latter, define "adjacent" for planets. >> The one-dimensional case is easy; the devil picks a sufficiently large >>distance from the angel at the initial point, methodically destroys >>100 planets in a line, watches the angel hop wherever she pleases, repeats >>the same on the other side, then entraps her with a random squeeze between >>the barriers. >> -- James A. Woods (ames!jaw) > >Surely this wouldn't work? The angel could travel parallel to the devil's >destruction line faster than the devil can destroy planets, and thus >escape out of the ends of the barriers. Key words: "one-dimensional case." The devil can actually do better in this case: Destroy 100 planets in a row, centered on the angels start point. Now, destroy one hundred planets in a row between 10,000 and 10,100 planets away from the angel in the direction away from the first patch of non-planets.