Date: Thu, 8 Jan 2004 14:57:36 -0500 (EST)
From: Dan Hoey <Hoey@aic.nrl.navy.mil>
To: Michael B Greenwald <mbgreen@central.cis.upenn.edu>
Subject: Re: [math-fun] Secret Santa problem
cc: math-fun <math-fun@mailman.xmission.com>

   Thu, 08 Jan 2004 11:18:25 -0800
   Marc LeBrun <mlb@fxpt.com>

   Can you think of a way to generate secret derangements that's about as
   natural as drawing names from a hat?

   Thu, 08 Jan 2004 14:44:12 EST
   Michael B Greenwald <mbgreen@central.cis.upenn.edu>

   Drawing names from two hats?  Split the names randomly,
   partitioning the group into reds and greens....

If the population is odd, partition the group into [n/3] reds,
[(n+1)/3] greens, and [(n+2)/3] yellows.  Yellows put their names into
the red hat, with excess into the green; reds put their names into the
green hat, with excess into the yellow; greens put their names into
the yellow hat.  Then each person draws from their own color of hat.

That unfortunately removes the mystery from trios and the red member
of quintets.  And it spoils the seasonal color scheme.

Dan