For Example,we shall be discussing graphs which cintain paths which include every edge or every vertex exactly once,ending upa at the initial vertex;

• 例如，我们将讨论这样一些图，图中存在包含所有边或所有顶点一次且仅一次而回到出发顶点的路，我们分别称之为欧拉图和哈密尔顿图。