Left examples are called "Eulerian graphs."
A connected graph is Eulerian if and only if each vertex is incident to an even number of edges.
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precise, allsorted, math, traditional, preciseworld
connected_graph [smaller | same | bigger]
Aaron David Fairbanks
https://en.wikipedia.org/wiki/Graph_theory
https://en.wikipedia.org/wiki/Connectivity_(graph_theory)
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precise, allsorted, world, preciseworld
graph [smaller | same | bigger]zoom in left (connected_graph) | zoom in right (disconnected_graph)
Leo Crabbe