chore: update lc problems (doocs#1379)

Author: yanglbme

solution/0000-0099/0021.Merge Two Sorted Lists/README_EN.md

@@ -6,7 +6,7 @@
 
 <p>You are given the heads of two sorted linked lists <code>list1</code> and <code>list2</code>.</p>
 
-<p>Merge the two lists in a one <strong>sorted</strong> list. The list should be made by splicing together the nodes of the first two lists.</p>
+<p>Merge the two lists into one <strong>sorted</strong> list. The list should be made by splicing together the nodes of the first two lists.</p>
 
 <p>Return <em>the head of the merged linked list</em>.</p>
 

solution/0100-0199/0104.Maximum Depth of Binary Tree/README.md

@@ -6,22 +6,38 @@
 
 <!-- 这里写题目描述 -->
 
-<p>给定一个二叉树，找出其最大深度。</p>
+<p>给定一个二叉树 <code>root</code> ，返回其最大深度。</p>
 
-<p>二叉树的深度为根节点到最远叶子节点的最长路径上的节点数。</p>
+<p>二叉树的 <strong>最大深度</strong> 是指从根节点到最远叶子节点的最长路径上的节点数。</p>
 
-<p><strong>说明:</strong>&nbsp;叶子节点是指没有子节点的节点。</p>
+<p>&nbsp;</p>
 
-<p><strong>示例：</strong><br>
-给定二叉树 <code>[3,9,20,null,null,15,7]</code>，</p>
+<p><strong>示例 1：</strong></p>
 
-<pre>    3
-   / \
-  9  20
-    /  \
-   15   7</pre>
+<p><img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0100-0199/0104.Maximum%20Depth%20of%20Binary%20Tree/images/tmp-tree.jpg" style="width: 400px; height: 277px;" /></p>
 
-<p>返回它的最大深度&nbsp;3 。</p>
+<p>&nbsp;</p>
+
+<pre>
+<b>输入：</b>root = [3,9,20,null,null,15,7]
+<b>输出：</b>3
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<b>输入：</b>root = [1,null,2]
+<b>输出：</b>2
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li>树中节点的数量在&nbsp;<code>[0, 10<sup>4</sup>]</code>&nbsp;区间内。</li>
+	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
+</ul>
 
 ## 解法