题目
非递归后序遍历
代码
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def postorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
stack = []
res = []
p = root
visited = None
while p!=None or len(stack)!=0:
while p!= None:
stack.append(p)
p = p.left
p = stack[-1]
if p.right==None or visited==p.right:
p = stack.pop()
visited = p
res.append(p.val)
p = None
else:
p = p.right
return res
