二叉树的深度

题目：Maximum Depth of Binary Tree

题目详情:

Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

翻译：

有一个二叉树，得到它的最大深度

答案：

/**
 * Definition for a binary tree node.
 * 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;
        else {
            int leftDepth = maxDepth(root.left);
            int rightDepth = maxDepth(root.right);
            return 1 + Math.max(leftDepth, rightDepth);
        }
    }
}