mirror of
https://github.com/prdlk/leetcode.git
synced 2026-11-02 13:12:44 +00:00
55 lines
1.3 KiB
Plaintext
55 lines
1.3 KiB
Plaintext
---
|
|
title: '104. Maximum Depth of Binary Tree'
|
|
description: Given the root of a binary tree, return its maximum depth
|
|
icon: dot
|
|
topics:
|
|
- { name: "Tree", slug: "tree" }
|
|
- { name: "Depth-First Search", slug: "depth-first-search" }
|
|
- { name: "Breadth-First Search", slug: "breadth-first-search" }
|
|
- { name: "Binary Tree", slug: "binary-tree" }
|
|
video: "hTM3phVI6YQ"
|
|
sidebar:
|
|
label: 'Maximum Depth of Binary Tree'
|
|
badge: 'Easy'
|
|
---
|
|
|
|
### 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, 10^4].
|
|
- `-100 <= Node.val <= 100`
|
|
|
|
## Approach
|
|
|
|
```mermaid
|
|
flowchart TD
|
|
S(["maxDepth(root)"]) --> B{"root is None?"}
|
|
B -- yes --> Z(["return 0"])
|
|
B -- no --> L["l = maxDepth(root.left), r = maxDepth(root.right)"]
|
|
L --> E(["return 1 + max(l, r) — this node adds one level above its deeper subtree"])
|
|
```
|
|
|
|
## Solution
|
|
|
|
```py
|
|
# 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
|
|
class Solution:
|
|
def maxDepth(self, root: Optional[TreeNode]) -> int:
|
|
if not root:
|
|
return 0
|
|
|
|
return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))
|
|
```
|