binarytree二叉树节点DFS深度优先搜索遍历，基于栈，非递归，python
注意对已经访问过的节点的处理，在while循环中，如果在栈回退时候，遇到之前访问过的节点，则直接弹出。弹出的情况还有一种就是该节点没有左右子节点了，表明到了尽头。
from binarytree import bst
def app():
t = bst(height=3, is_perfect=True)
print(t)
print('-----')
dfs(t)
def dfs(node):
if node.left is None and node.right is None:
return node
stack = [node]
visited = []
while True:
if len(stack) == 0:
break
visit_node = stack.pop()
visited.append(visit_node)
right_child = visit_node.right
left_child = visit_node.left
if right_child is not None:
stack.append(right_child)
if left_child is not None:
stack.append(left_child)
print('dfs', visited)
if __name__ == '__main__':
app()
输出：
______7_______
/ \
__3__ ___11___
/ \ / \
1 5 9 _13
/ \ / \ / \ / \
0 2 4 6 8 10 12 14
-----
dfs [Node(7), Node(3), Node(1), Node(0), Node(2), Node(5), Node(4), Node(6), Node(11), Node(9), Node(8), Node(10), Node(13), Node(12), Node(14)]
