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by thaumasiotes
763 days ago
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> the "3 houses with 3 utilities without crossing" puzzle In graph theory's terminology, this is "K3,3", one of two irreducible nonplanar graphs. The other one is K5. You can also make all the connections without crossing any edges if you embed the graph in a torus, which is equivalent to building a bridge over some set of edges that other edges are allowed to take. |
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