# Leetcode 104 - Maximum depth of binary tree

`Note`

- Use recursion is quicker.
- Because we are returning a
`number`

. The termination condition must`return 0`

.

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] |

1 | /** |