# 0111. Minimum Depth of Binary Tree

https://leetcode.com/problems/minimum-depth-of-binary-tree

## Description

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

**Note:** A leaf is a node with no children.

**Example 1:**

![](https://assets.leetcode.com/uploads/2020/10/12/ex_depth.jpg)

```
**Input:** root = [3,9,20,null,null,15,7]
**Output:** 2
```

**Example 2:**

```
**Input:** root = [2,null,3,null,4,null,5,null,6]
**Output:** 5
```

**Constraints:**

* The number of nodes in the tree is in the range `[0, 105]`.
* `-1000 <= Node.val <= 1000`

## ac

```java
```
