# N-Ary Tree Postorder Traversal Problem

## Description

LeetCode Problem 590.

Given the root of an n-ary tree, return the postorder traversal of its nodes’ values.

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

Example 1:

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

Example 2:

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

Constraints:

• The number of nodes in the tree is in the range [0, 10^4].
• 0 <= Node.val <= 10^4
• The height of the n-ary tree is less than or equal to 1000.

## Sample C++ Code

``````1
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/*
// 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:
vector<int> postorder(Node* root) {
vector<int> post;
vector<int> child;
if (root == NULL)
return post;
for (int i = 0; i < root->children.size(); i ++) {
child = postorder(root->children[i]);
post.insert(post.end(), child.begin(), child.end());
}
post.push_back(root->val);
return post;
}
};
``````