diff --git a/solution/0500-0599/0563.Binary Tree Tilt/README_EN.md b/solution/0500-0599/0563.Binary Tree Tilt/README_EN.md
index 818f0d44432be..1d0c5c2cc84c2 100644
--- a/solution/0500-0599/0563.Binary Tree Tilt/README_EN.md
+++ b/solution/0500-0599/0563.Binary Tree Tilt/README_EN.md
@@ -28,7 +28,7 @@ tags:
Input: root = [1,2,3]
Output: 1
-Explanation:
+Explanation:
Tilt of node 2 : |0-0| = 0 (no children)
Tilt of node 3 : |0-0| = 0 (no children)
Tilt of node 1 : |2-3| = 1 (left subtree is just left child, so sum is 2; right subtree is just right child, so sum is 3)
@@ -40,7 +40,7 @@ Sum of every tilt : 0 + 0 + 1 = 1
Input: root = [4,2,9,3,5,null,7]
Output: 15
-Explanation:
+Explanation:
Tilt of node 3 : |0-0| = 0 (no children)
Tilt of node 5 : |0-0| = 0 (no children)
Tilt of node 7 : |0-0| = 0 (no children)
diff --git a/solution/3400-3499/3421.Find Students Who Improved/README.md b/solution/3400-3499/3421.Find Students Who Improved/README.md
new file mode 100644
index 0000000000000..49310b9f66563
--- /dev/null
+++ b/solution/3400-3499/3421.Find Students Who Improved/README.md
@@ -0,0 +1,151 @@
+---
+comments: true
+difficulty: 中等
+edit_url: https://github.com/doocs/leetcode/edit/main/solution/3400-3499/3421.Find%20Students%20Who%20Improved/README.md
+tags:
+ - 数据库
+---
+
+
+
+# [3421. 查找进步的学生](https://leetcode.cn/problems/find-students-who-improved)
+
+[English Version](/solution/3400-3499/3421.Find%20Students%20Who%20Improved/README_EN.md)
+
+## 题目描述
+
+
+
+表：Scores
+
+
++-------------+---------+
+| Column Name | Type |
++-------------+---------+
+| student_id | int |
+| subject | varchar |
+| score | int |
+| exam_date | varchar |
++-------------+---------+
+(student_id, subject, exam_date) 是这张表的主键。
+每一行包含有关学生在特定考试日期特定科目成绩的信息。分数范围从 0 到 100（包括边界）。
+
+
+编写一个解决方案来查找 进步的学生。如果 同时 满足以下两个条件，则该学生被认为是进步的：
+
+
+ - 在 同一科目 至少有两个不同日期的考试。
+ - 他们在该学科 最近的分数 比他们 第一次的分数更高。
+
+
+返回结果表以 student_id，subject 升序 排序。
+
+结果格式如下所示。
+
+
+
+示例：
+
+
+
输入：
+
+
Scores 表：
+
+
++------------+----------+-------+------------+
+| student_id | subject | score | exam_date |
++------------+----------+-------+------------+
+| 101 | Math | 70 | 15-01-2023 |
+| 101 | Math | 85 | 15-02-2023 |
+| 101 | Physics | 65 | 15-01-2023 |
+| 101 | Physics | 60 | 15-02-2023 |
+| 102 | Math | 80 | 15-01-2023 |
+| 102 | Math | 85 | 15-02-2023 |
+| 103 | Math | 90 | 15-01-2023 |
+| 104 | Physics | 75 | 15-01-2023 |
+| 104 | Physics | 85 | 15-02-2023 |
++------------+----------+-------+------------+
+
+
+
输出：
+
+
++------------+----------+-------------+--------------+
+| student_id | subject | first_score | latest_score |
++------------+----------+-------------+--------------+
+| 101 | Math | 70 | 85 |
+| 102 | Math | 80 | 85 |
+| 104 | Physics | 75 | 85 |
++------------+----------+-------------+--------------+
+
+
+
解释：
+
+
+ - 学生 101 的数学：从 70 分进步到 85 分。
+ - 学生 101 的物理：没有进步（从 65 分退步到 60分）
+ - 学生 102 的数学：从 80 进步到 85 分。
+ - 学生 103 的数学：只有一次考试，不符合资格。
+ - 学生 104 in Physics：从 75 分进步到 85 分。
+
+
+
结果表以 student_id，subject 升序排序。
+
Table: Scores
+
+
++-------------+---------+
+| Column Name | Type |
++-------------+---------+
+| student_id | int |
+| subject | varchar |
+| score | int |
+| exam_date | varchar |
++-------------+---------+
+(student_id, subject, exam_date) is the primary key for this table.
+Each row contains information about a student's score in a specific subject on a particular exam date. score is between 0 and 100 (inclusive).
+
+
+Write a solution to find the students who have shown improvement. A student is considered to have shown improvement if they meet both of these conditions:
+
+
+ - Have taken exams in the same subject on at least two different dates
+ - Their latest score in that subject is higher than their first score
+
+
+Return the result table ordered by student_id, subject in ascending order.
+
+The result format is in the following example.
+
+
+Example:
+
+
+
Input:
+
+
Scores table:
+
+
++------------+----------+-------+------------+
+| student_id | subject | score | exam_date |
++------------+----------+-------+------------+
+| 101 | Math | 70 | 15-01-2023 |
+| 101 | Math | 85 | 15-02-2023 |
+| 101 | Physics | 65 | 15-01-2023 |
+| 101 | Physics | 60 | 15-02-2023 |
+| 102 | Math | 80 | 15-01-2023 |
+| 102 | Math | 85 | 15-02-2023 |
+| 103 | Math | 90 | 15-01-2023 |
+| 104 | Physics | 75 | 15-01-2023 |
+| 104 | Physics | 85 | 15-02-2023 |
++------------+----------+-------+------------+
+
+
+
Output:
+
+
++------------+----------+-------------+--------------+
+| student_id | subject | first_score | latest_score |
++------------+----------+-------------+--------------+
+| 101 | Math | 70 | 85 |
+| 102 | Math | 80 | 85 |
+| 104 | Physics | 75 | 85 |
++------------+----------+-------------+--------------+
+
+
+
Explanation:
+
+
+ - Student 101 in Math: Improved from 70 to 85
+ - Student 101 in Physics: No improvement (dropped from 65 to 60)
+ - Student 102 in Math: Improved from 80 to 85
+ - Student 103 in Math: Only one exam, not eligible
+ - Student 104 in Physics: Improved from 75 to 85
+
+
+
Result table is ordered by student_id, subject.
+