On page 102, we defined the binary relation “connected” on the set of vertices of a directedgraph. Show that this is an equivalence relation(see Exercise 3.29), and conclude that it partitions the vertices into disjoint strongly connected components.

Short Answer

Expert verified

It can be shown that the binary relation “connected” on the set of vertices of a directed graph is an equivalence relation and yes, it partitions the vertices into disjoint strongly connected components.

Step by step solution

01

Explain the Equivalence relation

A relation is said to be in equivalence only if the relation satisfies reflexive, symmetry, and transitive properties.

02

Show that the given relation is the equivalence relation

Consider a set S that has the partitions of an undirected graph. Consider any two vertices x and y in the undirected graph.

From the solution of Exercise 3.29, the binary connected relation of the connected relationship satisfies reflexivity, symmetry, and transitivity. So, it is an equivalence relation.

The strongly connected component is the equivalence class corresponding to this relation.

Thus, it partitions the vertices into disjoint strongly connected components.

Therefore, It is shown that the binary relation “connected” on the set of vertices of a directed graph is an equivalence relation and yes, it partitions the vertices into disjoint strongly connected components.

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Most popular questions from this chapter

Perform depth-first search on each of the following graphs; whenever there’s a choice of vertices, pick the one that is alphabetically first. Classify each edge as a tree edge, forward edge, back edge, or cross edge, and give the pre and post number of each vertex.

Question:Undirected vs. directed connectivity.

(a) Prove that in any connected undirected graph G =(V , E)there is a vertexvV whose removal leaves G connected. (Hint: Consider the DFS search tree for G.)

(b) Give an example of a strongly connected directed graph G(V ,E)such that, for everyvV, removing v from G leaves a directed graph that is not strongly connected.

(c) In an undirected graph with two connected components it is always possible to make the graph connected by adding only one edge. Give an example of a directed graph with two strongly connected components 0 such that no addition of one edge can make the graph strongly connected.

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  1. If p is an infinite trace, let Inf(p)V be the set of vertices that occur infinitely often in p. Show that Inf(p) is a subset of a strongly connected component of G.
  2. Describe an algorithm that determines if role="math" G has an infinite trace.
  3. Describe an algorithm that determines if G has an infinite trace that visits some good vertex in VG infinitely often.
  4. Describe an algorithm that determines if role="math" localid="1659627728759" G has an infinite trace that visits some good vertex in VG infinitely often, but visits no bad vertex in VB infinitely often.

Give a linear-time algorithm for the following task.
Input: A directed acyclic graph G

Does G contain a directed path that touches every vertex exactly once?

Either prove or give a counterexample: if {u,v}is an edge in an undirected graph, and during depth-first search (u)<post (v), then vis an ancestor of uin the DFS tree.

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