topological sort

toposort.py

E = { "A": ["E"], 
      "B": ["A", "C", "G"], 
      "C": ["A"], 
      "D": ["B", "G"], 
      "E": ["F"], 
      "F": [], 
      "G": ["A", "F"], 
    }


class Toposort:
  def __init__(self):
    self.visited = []

  def DFS(self, node, graph):
    for x in graph.get(node, []):
      if x not in self.visited:
        self.DFS(x, graph)
    self.visited = [node] + self.visited

  def toposort(self, graph):
    for node in graph:
      if node not in self.visited:
        self.DFS(node, graph)
    return self.visited

if __name__ == "__main__":
  ts = Toposort()
  print(ts.toposort(E))