[techtalk] This talk of N-ary trees and other things...

David Merrill david at lupercalia.net
Fri Mar 23 22:02:41 EST 2001

On Fri, Mar 23, 2001 at 08:43:24PM -0500, David Merrill wrote:
> On Fri, Mar 23, 2001 at 04:54:47PM -0800, Nancy Corbett wrote:
> > 
> > ---
> > Knights and Knaves problem. 
> > 
> > Suppose you visit a strange island with three types of people. Knights,
> > who always tell the truth, Knaves, who always lie and Normals who
> > sometimes lie and sometimes tell the truth. It is also the custom that
> > normals marry only normals, and knights marry only knaves. 
> > You meet two couples, Mr. and Mrs. Smith and Mr. and Mrs. Brown. They tell
> > you the following: 
> > 
> > Mr. Brown: Mr. Smith is a knight. 
> > Mrs. Brown: My husband is right, Mr. Smith is  a knight. 
> > Mrs. Smith: That?s true, my husband is indeed a knight. 
> > 
> > Can you determine which type each person must be? Explain.
> > ---
> Hmmmmm.
> Mr. and Mrs. Brown are normals. A knight and a knave would not agree.
> If Mrs. Smith were a knave, her husband would be a knight and she
> would not call him so. And if she were a knight, she would not call
> her knave husband a knight! So are they *all* normals?

No. You never said knaves marry only knights, only that knights marry
only knaves. So they could be either all normals, or else Mr. and Mrs.
Smith are both knaves. Two possible solutions, unless I'm still
missing something.

Wouldn't be the first time.

Dr. David C. Merrill                     http://www.lupercalia.net
Linux Documentation Project                   david at lupercalia.net
Collection Editor & Coordinator            http://www.linuxdoc.org
                                       Finger me for my public key

To err is human -- to blame it on a computer is even more so.

More information about the Techtalk mailing list