Chapter 4.13
Covering Problem

1. Vertex Cover: Given undirected graph, G = (V,E). There exists a subset A ⊆ V , such that A is a vertex cover, if every edges in G has at least one endpoint in A.
2. Given a set U of size n, and collections of subsets of S₁,…,S_m ⊆ U. There exists a subset C ⊆{1,…,m}, such that ⋃ _iCS_i = U.