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+19 votes

Let $G$ be a simple graph with $20$ vertices and $100$ edges. The size of the minimum vertex cover of G is $8$. Then, the size of the maximum independent set of $G$ is:

  1. $12$
  2. $8$
  3. less than $8$
  4. more than $12$
asked in Graph Theory by Boss (18.3k points)
edited by | 2.3k views

1 Answer

+38 votes
Best answer

Vertex cover: A set  of vertices such that each edge of the graph is incident to at least one vertex of the set.

Therefore, removing all the vertices of the vertex cover from the graph results in an isolated graph and the same set of nodes would be the independent set in the original graph.

Size of minimum vertex cover $= 8$
Size of maximum independent set $= 20 - 8  =12$

Therefore, correct answer would be (A).

Reference :-

answered by Loyal (5.8k points)
edited by
Well explained!!
a set of vertices $X \subseteq V(G)$ of a graph $G$ is independent if and only if its complement $V(G) \setminus X$ is a vertex cover.   ( $V(G) \setminus X$ is complement of $X$ )
(Because if $X$ is VC, then for every edge atleast one endpoint will be in $X$. Removing $X$ from $V$ we get all nonadjacent vertices.)
Complement of vertex cover is Independent set and vice versa.
If that vertex cover is minimum, then complement is Maximum Independent set.
nice explanation !!!

always searching of ur comment / answer :)
vertex covering no. + vertex independent no. = no. of vertices

8 + vertex independent no. = 20

vertex independent no.= 12
He he..thnks Anil :)

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