title: find the minimum size dominating set for a tree using greedy algorithm
body: <p>Dominating Set (DS) := given an undirected graph G = (V;E), a set of
  vertices S  V is a dominating set if for every vertex in V , there is a vertex in
  S that is adjacent to v. Entire vertex set V is a trivial dominating set in
  any graph. </p>
  
  <p>Find minimum size dominating set for a tree.</p>