1. The document discusses Hamiltonian and Euler circuits in graphs. It defines Hamiltonian and Euler paths and circuits, noting that Hamiltonian circuits visit every vertex once while Euler circuits use every edge once.
2. Hamiltonian and Euler problems deal with finding paths between vertices that meet certain criteria. No simple test exists to determine Hamiltonian paths, but certain conditions like having a degree-1 vertex rule out Hamiltonian circuits.
3. Applications of Hamiltonian and Euler problems include computer graphics, circuit design, genome mapping, and transportation planning.