590题

方法一：递归

// 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) {
        if(root==NULL){
            return result;
        }
        for(auto&it:root->children){
            postorder(it);
        }
        result.push_back(root->val);
        return result;
    }
    vector<int>result;
};