title: Topological sort for adjacency Matrix
body: <p>Given a graph represented as an adjacency matrix, how can I do a topological sort in linear time?
  Even if I do a preprocessor to create an array of the in-degree value it will be with the time complexity of O(|V|^2).
  I know that for a topological sort from a matrix it is possible to create an algorithm of linear time, so what am I missing? </p>