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MathGroup Archive 2010

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Directed Hamiltonian Cycles

  • To: mathgroup at smc.vnet.net
  • Subject: [mg109172] Directed Hamiltonian Cycles
  • From: J Siehler <jsiehler at gmail.com>
  • Date: Wed, 14 Apr 2010 23:14:19 -0400 (EDT)

I could be overlooking something, but there seems to be no mention in
the documentation (Version 7.0) that HamiltonianCycle and HamiltonianQ
do not work properly for directed graphs.  Not only that, they fail in
a misleading way, returning a result with no warning that it's
probably bogus.  This is noted in the MathWorld page on Hamiltonian
Cycles (http://mathworld.wolfram.com/HamiltonianCycle.html), but
perhaps the fact could be noted more clearly in the documentation for
these functions?

In[22]:= FromOrderedPairs[{{1,2},{2,3},{3,1}}]
HamiltonianQ[%]

Out[22]=Graph:<3,3,Directed >
Out[23]= False


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