思路:
1. 使用列表保存结果;
2. 使用栈(列表实现)存储结点;
3. 当根结点存在,保存结果,根结点入栈;
4. 将根结点指向左子树;
5. 根结点不存在,栈顶元素出栈,并将根结点指向栈顶元素的右子树;
6. 重复步骤3-6,直到栈空。
LeetCode: 144. Binary Tree Preorder Traversal
# 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]
"""
ret = []
stack = []
while root or stack:
while root:
ret.append(root.val)
stack.append(root)
root = root.left
if stack:
t = stack.pop()
root = t.right
return ret
时间: 2024-11-08 23:44:49