package tree;

import java.util.LinkedList;

import java.util.List;

import java.util.Queue;

public class MaxDepth {

    public int maxDepth(Node root) {

        if(root==null)

            return 0;

        int height =0;

        Queue<Node> queue = new LinkedList<Node>();

        queue.add(root);

        int size = queue.size();

        while (!queue.isEmpty())

        {

           Node tmp =  queue.poll();

           for(Node node:tmp.children)

               if(node!=null)

                    queue.add(node);

            size--;

            if(size==0)

            {

                size=queue.size();

                height++;

            }

        }

        return height;

    }

}

// Definition for a Node.

class Node {

    public int val;

    public List<Node> children;

    public Node() {}

    public Node(int _val,List<Node> _children) {

        val = _val;

        children = _children;

    }

};