Provide an O(|V|) algorithm that solves the following problem.
given: a directed graph G = (V,E), represented as an adjacency
matrix. task: determine whether or not there is a vertex w ∈ V such
that, for every other vertex v ∈ V with v 6= w, we have: (v,w) ∈ E
but (w,v) / ∈ E