摘要：
Trail: a walk that does not repeat any edges.Closed Trail(Circuit): a trail that begins and ends at the same vertex.Eulerian Circuit: a circuit that includes every edge of the graph.Eulerian Trail: a trail that includes every edge of the graph.在无向图中，图 $G$ 有欧拉回路当且仅当每个点的度数为偶数。在有向图中，图 $G$ 有欧拉回路当且仅当每个点的 阅读全文