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    • ▾Graph theory
      • •Matchings
      • •Minimum spanning tree
      • •Automorphisms of a graph
      • •Tournament graphs
      • ▸Basics of graph theory
        • •Intro to graphs
        • •Isomorphic graphs
        • •Walks, paths, and cycles
        • •Connected graphs
        • •Adjacency and degrees
        • •Subgraphs
        • •Graph components
        • •Adjacency lists, adjacency matrices, and incidence matrices
        • •Other simple planar graphs
        • •Regular graphs
      • •Intro to bipartite graphs
      • ▸Paths and cycles
        • ▸Eulerian cycles and paths
          • •Intro
          • •Using the theorem
        • •Hamiltonian cycles and paths
      • •Planar graphs
      • ▸Coloring
        • •Intro to vertex colorings
      • •Dijkstra's algorithm
      • •Fleury's algorithm
      • •Flows and cuts
      • •Kruskal's algorithm
      • •Minimum vertex covers
      • •Number of edges in a complete graph
      • •Perfect graph
      • •Size of tree is one less than order
      • ▸Trees
        • •Intro to trees
        • •Proving properties of trees
      • •Utilities puzzle
      • •What is a complete graph?
      • •What is a cubic graph?
      • •What is a maximal clique?
      • •What is an edge-induced subgraph?
      • •What is an irregular graph?
      • •What is a spanning subgraph?
      • •What is a vertex-induced subgraph?
      • •Intro to digraphs
      • •Combinatorics and graph theory
      • •Graceful labeling
     › Graph theory

    Paths and cycles

    1. Eulerian cycles and paths
    2. Hamiltonian cycles and paths
    A nontrivial connected graph is Eulerian if and only if every vertex has even degree.
    70468Proof: Graph is Eulerian iff All Vertices have Even Degree | Euler Circuits, Graph Theory
    Wrath of Math
    A connected graph has an Euler trail if and only if it has at most 2 vertices of odd degree.
    70369Graph Theory: 24. Euler Trail iff 0 or 2 Vertices of Odd Degree
    Sarada Herke