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# 111. Minimum Depth of Binary Tree

## Easy

***

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)

<pre><code>Input: root = [3,9,20,null,null,15,7]
<strong>Output:
</strong> 2
</code></pre>

**Example 2:**

<pre><code>Input: root = [2,null,3,null,4,null,5,null,6]
<strong>Output:
</strong> 5
</code></pre>

&#x20;

**Constraints:**

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