Hamiltonian

graph theory began in 1736 when euler noticed that a walking-tour puzzle about seven bridges in königsberg was really a question about dots and lines — and that the geometry (lengths, positions, the river) was irrelevant. 𐃏 that act of abstraction — keep the incidence structure, discard everything else — is the whole subject. a graph is the minimal mathematical model of “things, some pairs of which are related”, which is why it keeps turning up: networks, molecules, dependencies, state machines, social graphs (Epp, Susanna S., 2019).