Completely re-engineered version of Loopy, courtesy of Lambros
Lambrou. Now capable of handling triangular and hexagonal grids as
well as square ones, and then a number of semiregular plane tilings
and duals of semiregular ones. In fact, most of the solver code
supports an _arbitrary_ planar graph (well, provided both the graph
and its dual have no self-edges), so it could easily be extended
further with only a little more effort.
git-svn-id: svn://svn.tartarus.org/sgt/puzzles@8162
cda61777-01e9-0310-a592-
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