

We briefly mentioned that a graph contains sets of vertices and edges: there is no implicit ordering among the edges associated with a vertex, or among the vertices in a graph. The Graph classes use the Set(C++). library extensively to represent the sets of information associated with a Graph. Specifically, since the Graph manipulates pointers to Vertices and Edges, Set_of_p (which is a set of pointers) is used.
We'll use Sets to help answer the second question from the section, ``Example: Manufacturing Process of a Widget''.