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55 lines
1.3 KiB
Plaintext
55 lines
1.3 KiB
Plaintext
---
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title: '104. Maximum Depth of Binary Tree'
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description: Given the root of a binary tree, return its maximum depth
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icon: dot
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topics:
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- { name: "Tree", slug: "tree" }
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- { name: "Depth-First Search", slug: "depth-first-search" }
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- { name: "Breadth-First Search", slug: "breadth-first-search" }
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- { name: "Binary Tree", slug: "binary-tree" }
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video: "hTM3phVI6YQ"
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sidebar:
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label: 'Maximum Depth of Binary Tree'
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badge: 'Easy'
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---
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### Example 1:
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- Input: `root = [3,9,20,null,null,15,7]`
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- Output: `3`
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### Example 2:
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- Input: `root = [1,null,2]`
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- Output: `2`
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### Constraints:
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- The number of nodes in the tree is in the range [0, 10^4].
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- `-100 <= Node.val <= 100`
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## Approach
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```mermaid
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flowchart TD
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S(["maxDepth(root)"]) --> B{"root is None?"}
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B -- yes --> Z(["return 0"])
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B -- no --> L["l = maxDepth(root.left), r = maxDepth(root.right)"]
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L --> E(["return 1 + max(l, r) — this node adds one level above its deeper subtree"])
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```
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## Solution
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```py
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def maxDepth(self, root: Optional[TreeNode]) -> int:
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if not root:
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return 0
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return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))
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```
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