栈和队列_leetcode144-二叉树前序遍历非递归

# 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 preorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""

class Command(object):
def __init__(self,com,node):
self.com = com
self.node = node


res = []
stack = []

if not root:
return res
stack.append(Command("go",root))

while stack:
com = stack.pop()

if com.com == "print":
res.append(com.node.val)
else:
if com.node.right:
stack.append(Command("go",com.node.right))
if com.node.left:
stack.append(Command("go",com.node.left))
stack.append(Command("print",com.node))

return res
posted @ 2019-03-17 16:10  AceKo  阅读(198)  评论(0编辑  收藏  举报