[leetcode]Binary Tree Preorder Traversal

最新推荐文章于 2022-07-19 12:03:10 发布

aljjj

最新推荐文章于 2022-07-19 12:03:10 发布

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分类专栏： leetcode 文章标签： leetcode 数据结构二叉树

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本文介绍了一种实现二叉树先序遍历的非递归方法，并提供了一个使用Python实现的具体示例。

题目：

Given a binary tree, return the preorder traversal of its nodes' values.

For example:
Given binary tree {1,#,2,3},

return [1,2,3].

Note: Recursive solution is trivial, could you do it iteratively?

链接：https://oj.leetcode.com/problems/binary-tree-preorder-traversal/

描述：二叉树的先序遍历，非递归

solution by python:

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    # @param root, a tree node
    # @return a list of integers
    def preorderTraversal(self, root):
        if root == None: return []
        stk, ans = [], []
        p = root
        while p!=None or len(stk)!=0:
            if p == None:
                p = stk.pop().right
            else:
                ans.append(p.val)
                stk.append(p)
                p = p.left
        return ans