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Maximum Depth of Binary Tree

Given the root of a binary tree (as a level-order array), return its maximum depth (number of nodes along the longest root-to-leaf path).

Input:

3,9,20,null,null,15,7

Output:

Reasoning:

The input array represents a binary tree in level-order traversal: 3 is the root, 9 and 20 are its children, and 15 and 7 are the children of 20.
The tree structure is:
- 3 (root)
- / \
- 9 20
- / \
- 15 7
We calculate the depth of each path: the path 3 -> 9 has a depth of 2, and the path 3 -> 20 -> 15 (or 7) has a depth of 3.
The maximum depth among all paths is $3$ , which corresponds to the longest root-to-leaf path (3 -> 20 -> 15 or 3 -> 20 -> 7).
The final output is 3, representing the maximum depth of the binary tree.

Editor

Python 3.13.1

0/0

Run code to see test results.

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