/** * 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) { if(root == null) return 0; int nleft = maxDepth(root.left); int nright = maxDepth(root.right); return (nleft > nright) ? nleft+1 : nright+1; } }