Method add_edges

recipes/Python/576912_A_Tree_Finder/recipe-576912.py:65–70

(self, edges)

    self.roots = set()
    
  def add_edges(self, edges):
    if len(edges) != len(set(edges)):
      self.has_duplicate_edges = True
      
    for u,v in edges:
      self.inv_g.add_edge(v,u) # here, the most tricky part!!

  def find_roots(self, v, visited):
    ''' @return: False, if failed to find the root,