leetcode 104: Maximum Depth of Binary Tree

题目：

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.

思路：

对于某个节点，比较左右子数的深度，反复此过程。

编码：

/**
 * 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 lDepth = maxDepth(root.left);
            int rDepth = maxDepth(root.right);
            return lDepth > rDepth ? lDepth+1 : rDepth +1;
        }
    }
}