Hamiltonian problem
Hamiltonian cycle
Hamiltonian path
Hamiltonian tour
Hamilton's problem

    (Or "Hamilton's problem") A problem in graph
   theory posed by William Hamilton: given a graph, is there
   a path through the graph which visits each vertex precisely
   once (a "Hamiltonian path")?  Is there a Hamiltonian path
   which ends up where it started (a "Hamiltonian cycle" or
   "Hamiltonian tour")?

   Hamilton's problem is NP-complete.  It has numerous
   applications, sometimes completely unexpected, in computing.

   (http://ing.unlp.edu.ar/cetad/mos/Hamilton.html).

   (1997-07-18)