How many different digraphs are there on V vertices? Allow self-loops but do now allow self-edges.

Suppose that a digraph G is represented using the adjacency-lists representation. What is the order of growth of the running time to find all vertices that point to a given vertex v?

Suppose that during an execution of depth-first search in a digraph G, `dfs(v)` is called after `dfs(w)` is called, but before `dfs(w)` returns. Which of the following must be true of the graph G?

How many strong components does a DAG on V vertices and E edges have?