/*
// 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 {
    void preorder(vector<int> &traversal, Node *root) {
        if (root == nullptr) {
            return;
        }

        traversal.push_back(root->val);
        for (auto child : root->children) {
            preorder(traversal, child);
        }
    }

  public:
    vector<int> preorder(Node *root) {
        vector<int> result;
        preorder(result, root);
        return result;
    }
};