import java.util.*; /* * public class TreeNode { * int val = 0; * TreeNode left = null; * TreeNode right = null; * } */ public class Solution { /** * * @param root TreeNode类 * @return int整型 */ public int maxDepth (TreeNode root) { // write code here if(root == null) return 0; return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1; } }