Maximum Depth of Binary Tree in Java: Explanation & Practice

Find the maximum depth (height) of a binary tree

Problem summary

Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from root to a leaf.

Starter code

public class Main {
    public static void main(String[] args) {
        // Tree:     3
        //          / \
        //         9  20
        //            / \
        //           15  7
        // Print: Depth: 3
    }
}

Expected output and test cases

[3,9,20,null,null,15,7]
```
Depth: 3
```
[1,null,2]
```
Depth: 2
```
[] → 0
```
Depth: 0
```

Hints

Base case: null node has depth 0
Recursive: 1 + max(depth(left), depth(right))
Can also use BFS level-by-level counting
Each recursion adds 1 to the depth

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