递归求二叉树的最大深度。

       

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {   public int maxDepth(TreeNode root) {		 if(root == null)			 return 0;		 if(root == null)			 return 0;		 int l = maxDepth(root.left);		 int r = maxDepth(root.right);		 if(l > r) return l+1;		 else return r+1;	 }	 }