N 叉树的后序遍历

/*
// 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 helper(const Node*root,vector<int> & res)
    {
        if(root==nullptr)
        {
            return;
        }
         for(auto &ch:root->children)
         {
             helper(ch,res);
         }
         res.emplace_back(root->val);
    }
    vector<int> postorder(Node* root) {
        vector<int> res;
        helper(root,res);
        return res;
        
    }
 
};