Example: N‐Ary Postorder Traversal - rFronteddu/general_wiki GitHub Wiki

class Solution {
    public List<Integer> postorder(Node root) {
        List<Integer> result = new ArrayList<>();
        if (root == null) {
            return result;
        }
        
        helper(root, result);
        return result;
    }
    
    void helper(Node node, List<Integer> result) {
        for (var n : node.children) {
            helper(n, result);
        }
        result.add(node.val);
    }
}