每日一题：二叉树的最大深度问题

/**
 * 返回一棵树的最大深度、
 * 测试链接：https://leetcode.com/problems/maximum-depth-of-binary-tree
 */
public class Code03_MaximumDepthOfBinaryTree {
    public static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;
    }

    public static int maxDepth(TreeNode root){
        if (root == null){
            return 0;
        }
        return Math.max(maxDepth(root.left),maxDepth(root.right)) + 1;
    }
}