104.maximum-depth-of-binary-tree

Statement

简体中文English

Metadata

• Link: 二叉树的最大深度
• Difficulty: Easy
• Tag: 树 深度优先搜索 广度优先搜索 二叉树

给定一个二叉树，找出其最大深度。

二叉树的深度为根节点到最远叶子节点的最长路径上的节点数。

说明: 叶子节点是指没有子节点的节点。

示例：
给定二叉树 [3,9,20,null,null,15,7]，

    3
   / 

  9  20
    /  

   15   7

返回它的最大深度 3 。

Metadata

• Link: Maximum Depth of Binary Tree
• Difficulty: Easy
• Tag: Tree Depth-First Search Breadth-First Search Binary Tree

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

 

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: 3

Example 2:

Input: root = [1,null,2]
Output: 2

 

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• -100 <= Node.val <= 100

Solution

Python 3

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
from typing import Optional


class Solution:
    res = 0

    def dfs(self, rt: TreeNode, d: int) -> None:
        if not rt:
            return

        cur_d = d + 1
        self.res = max(self.res, cur_d)
        self.dfs(rt.left, cur_d)
        self.dfs(rt.right, cur_d)

    def maxDepth(self, root: Optional[TreeNode]) -> int:
        self.dfs(root, 0)
        return self.res

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最后更新: October 11, 2023