<p>Given an n-ary tree, return the <em>level order</em> traversal of its nodes' values.</p> <p><em>Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).</em></p> <p> </p> <p><strong>Example 1:</strong></p> <p><img src="https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png" style="width: 100%; max-width: 300px;" /></p> <pre> <strong>Input:</strong> root = [1,null,3,2,4,null,5,6] <strong>Output:</strong> [[1],[3,2,4],[5,6]] </pre> <p><strong>Example 2:</strong></p> <p><img alt="" src="https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png" style="width: 296px; height: 241px;" /></p> <pre> <strong>Input:</strong> root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14] <strong>Output:</strong> [[1],[2,3,4,5],[6,7,8,9,10],[11,12,13],[14]] </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li>The height of the n-ary tree is less than or equal to <code>1000</code></li> <li>The total number of nodes is between <code>[0, 10<sup>4</sup>]</code></li> </ul>