What is the number of unlabeled simple directed graph that can be made with 1 or 2 vertices?

Category: QuestionsWhat is the number of unlabeled simple directed graph that can be made with 1 or 2 vertices?
Editor">Editor Staff asked 4 weeks ago

What is the number of unlabeled simple directed graph that can be made with 1 or 2 vertices?
 
(a) 2
 
(b) 4
 
(c) 5
 
(d) 9
 
My enquiry is from Directed Graph in section Graph of Data Structures & Algorithms I
 
The question was posed to me in a job interview.

1 Answers
Editor">Editor Staff answered 4 weeks ago

Correct choice is (b) 4
 
Explanation: The number of unlabeled simple directed graph that can be made with 1 or 2 vertices is 4