<p>Given the <code>root</code> of an n-ary tree, return <em>the postorder traversal of its nodes&#39; values</em>.</p>

<p>Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples)</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img src="https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png" style="width: 100%; max-width: 300px;" />
<pre>
<strong>Input:</strong> root = [1,null,3,2,4,null,5,6]
<strong>Output:</strong> [5,6,3,2,4,1]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png" style="width: 296px; height: 241px;" />
<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> [2,6,14,11,7,3,12,8,4,13,9,10,5,1]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[0, 10<sup>4</sup>]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 10<sup>4</sup></code></li>
	<li>The height of the n-ary tree is less than or equal to <code>1000</code>.</li>
</ul>

<p>&nbsp;</p>
<p><strong>Follow up:</strong> Recursive solution is trivial, could you do it iteratively?</p>

/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> children;

    Node() {}

    Node(int _val) {
        val = _val;
    }

    Node(int _val, vector<Node*> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
public:
    unsigned msize = 40960;
    void postorder1(Node *root, vector<int> &acc) {
        if (root == nullptr)
            return;
        if (root->children.size() != 0)
            for (Node *child : root->children)
                postorder1(child,acc);
        acc.push_back(root->val);
    }

    vector<int> postorder(Node* root) {
        vector<int> acc;
        acc.reserve(1280000);
        postorder1(root, acc);
        return acc;
    }
};
39041