589. N-ary Tree Preorder Traversal

class Solution {
    List<Integer> result = new ArrayList<>();
    public List<Integer> preorder(Node root) {
        if(root == null) return result;
        preorderHelper(root);
        return result;
    }
    
    public void preorderHelper(Node node) {
        if(node.children == null) return;
        result.add(node.val);
        for(Node child : node.children) {
            preorderHelper(child);
        }
    }
}

class Solution {
    List<Integer> result = new ArrayList<>();
    public List<Integer> preorder(Node root) {
        if(root == null) return result;
        
        Stack<Node> stack = new Stack<>();
        stack.push(root);
        
        while(!stack.isEmpty()) {
            Node curr = stack.pop();
            result.add(curr.val);
            //Pushing in children in reverse order
            for(int i = curr.children.size()-1; i >= 0; i--) {
                stack.push(curr.children.get(i));
            }
        }
        
        return result;
    }
    
}}