104. Maximum Depth of Binary Tree

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.Note: A leaf is a node with no children.Example:Given binary tree [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7return its depth = 3.难度：easy题目：给定二叉树，找出最大深度。最大深度指的是最长路径从根结点到最远的叶子结点。思路：后序遍历Runtime: 0 ms, faster than 100.00% of Java online submissions for Maximum Depth of Binary Tree.Memory Usage: 27.8 MB, less than 73.06% of Java online submissions for Maximum Depth of Binary Tree./** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */class Solution { public int maxDepth(TreeNode root) { if (null == root) { return 0; } return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1; }}