#!/usr/bin/env python
# -*- coding: utf-8 -*-

def DFS(graph, root_node = "root"):

    stack = []
    children = graph[root_node]
    stack = children + stack
    print(root_node)

    while len(stack) > 0:
        node = stack.pop(0)
        print(node)
        children = graph[node]

        stack = children + stack

"""
example:

graph = {"a":["b", "c"], "b":["d", "e"], "c":[], "d":[], "e":[]}

DFS(graph, root_node = "a")
# a
# b
# d
# e
# c
"""