Given a weighted graph, find a Hamiltonian cycle (a cycle visiting every vertex exactly once) with the minimum total edge weight.
Given a weighted graph and two vertices, find the shortest path between them.
The Königsberg bridge problem, solved by Leonhard Euler in 1735, is a seminal problem in graph theory. The problem asks whether it's possible to traverse all seven bridges in Königsberg (now Kaliningrad) exactly once.