/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {


	   public int maxDepth(TreeNode root) {

		   List rst = new ArrayList();
	       List list = new ArrayList();
	       dfs(root,rst,list);

	       if(rst.size() == 0){
	    	   return 0;
	       }

	       int max=rst.get(0).size();
	       for(int i=1;i