590. N-ary Tree Postorder Traversal

/*
// 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:
 void check(Node* root,vector<int> &ans){
        if(root==NULL)
        return ;
        for (auto child : root -> children)
            check(child, ans);
         ans.push_back(root -> val);

    }
    vector<int> postorder(Node* root) {
        vector<int> ans;
        check(root,ans);
        return ans;
    }
};