Answer:
Check the explanation
Explanation:
It can be shown in the following way:
This solution needs to exhibit that the set H-one can easily verify in polynomial-time if H is of size k and intersects each of the sets B1.....Bm .
We reduce from Vertex Cover.Consider an instance of the Vertex-Cover problem graph G=(V,E) and a positive integer k.We map it to an instance of the hitting set problem as follows.The set A is of vertices V.For every edge e belongs to E we have a set Se Consisting of two end-points of e.It is easy to see that a set of vertices S is a vertex cover of G iff the corresponding elements from a hitting set in the hitting set instance.