N-ary Tree Level Order Traversal

Given an n-ary tree, return the level order traversal of its nodes' values (i.e., from left to right, level by level).

Each node in the tree has a val (integer) and a children (array of child nodes).

The nary-tree input serialization is represented in level order traversal, where each group of children is separated by the null value.

Examples

Example 1:

Input: root = [1, null, 3, 2, 4, null, 5, 6]

Output: [[1],[3,2,4],[5,6]]

Explanation:

• Level 0: [1]
• Level 1: [3, 2, 4]
• Level 2: [5, 6]

Example 2:

Input: 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]

Output: [[1],[2,3,4,5],[6,7,8,9,10],[11,12,13],[14]]

Example 3:

Input: root = []

Output: []

Constraints

• The height of the n-ary tree is less than or equal to 1000
• The total number of nodes is in the range [0, 10⁴]
• Each node's value is in the range [0, 10⁴]