LeetCode 1522 Diameter of N-ary Tree

Base question: LC543 diameter of binary tree, LC1245 tree diameter.
diameter of binary tree are solved using recursion, we use a global max, and we get the maxdepth of left and maxdepth of right subtree, and we always maintain this global maximal.
tree diameter, now, this tree is very much like a graph, but it’s still a tree, it’s very much like this N-ary tree. so what’s the difference between them? the input.
the input of that tree diameter is int[][] edges, it has no root, it can be start from any node.
the input of this N-ary diameter is Node root.

there are some similarity between this code and that tree diameter, pay attention to that.

class Solution {
    private int diameter = 0;
    public int diameter(Node root) {
        height(root);
        return diameter;
    }
    
    private int height(Node node) { //the maximum height based on current node as root
        if (node.children.size() == 0) return 0;
        
        int maxHeight1st = 0;
        int maxHeight2nd = 0;
        for (Node child: node.children) {
            int parentHeight = height(child) + 1; //the height of parent of current child node
            if (parentHeight > maxHeight1st) {
                maxHeight2nd = maxHeight1st;
                maxHeight1st = parentHeight;
            } else if (parentHeight > maxHeight2nd) {
                maxHeight2nd = parentHeight;
            }
            
            int distance = maxHeight1st + maxHeight2nd; //the number of edges on this route
            diameter = Math.max(diameter, distance);
            
        }
        return maxHeight1st;
    }
}