minimum-depth-of-binary-tree.md

<p>Given a binary tree, find its minimum depth.</p>

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

<p><strong>Note:</strong>&nbsp;A leaf is a node with no children.</p>

<p><strong>Example:</strong></p>

<p>Given binary tree <code>[3,9,20,null,null,15,7]</code>,</p>

<pre>
    3
   / \
  9  20
    /  \
   15   7</pre>

<p>return its minimum&nbsp;depth = 2.</p>