Example: N‐Ary preorder traversal - rFronteddu/general_wiki GitHub Wiki

class Solution {
    public List<Integer> preorder(Node root) {
        List<Integer> result = new ArrayList<>();
        if (root == null) {
            return result;
        }
        preorderHelper (root, result);
        return result;
    }
    
    void preorderHelper(Node node, List<Integer> result) {
        result.add(node.val);
        
        for (int i = 0; i < node.children.size(); i++) {
            preorderHelper(node.children.get(i), result);
        }
    }
}