feat: add solutions to lc problem: No.3436

solution/3400-3499/3436.Find Valid Emails/README.md

@@ -0,0 +1,125 @@
+---
+comments: true
+difficulty: 简单
+edit_url: https://github.com/doocs/leetcode/edit/main/solution/3400-3499/3436.Find%20Valid%20Emails/README.md
+tags:
+    - 数据库
+---
+
+<!-- problem:start -->
+
+# [3436. Find Valid Emails](https://leetcode.cn/problems/find-valid-emails)
+
+[English Version](/solution/3400-3499/3436.Find%20Valid%20Emails/README_EN.md)
+
+## 题目描述
+
+<!-- description:start -->
+
+<p>Table: <code>Users</code></p>
+
+<pre>
++-----------------+---------+
+| Column Name     | Type    |
++-----------------+---------+
+| user_id         | int     |
+| email           | varchar |
++-----------------+---------+
+(user_id) is the unique key for this table.
+Each row contains a user&#39;s unique ID and email address.
+</pre>
+
+<p>Write a solution to find all the <strong>valid email addresses</strong>. A valid email address meets the following criteria:</p>
+
+<ul>
+	<li>It contains exactly one <code>@</code> symbol.</li>
+	<li>The part before the <code>@</code> symbol contains only <strong>alphanumeric</strong> characters and <strong>underscores</strong>.</li>
+	<li>The part after the <code>@</code> symbol contains a domain name <strong>that starts with a letter</strong> and ends with <code>.com</code>.</li>
+</ul>
+
+<p>Return<em> the result table ordered by</em> <code>user_id</code> <em>in</em> <strong>ascending </strong><em>order</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong></p>
+
+<p>Users table:</p>
+
+<pre class="example-io">
++---------+---------------------+
+| user_id | email               |
++---------+---------------------+
+| 1       | alice@example.com   |
+| 2       | bob_at_example.com  |
+| 3       | charlie@example.net |
+| 4       | david@domain.com    |
+| 5       | eve@invalid         |
++---------+---------------------+
+</pre>
+
+<p><strong>Output:</strong></p>
+
+<pre class="example-io">
++---------+-------------------+
+| user_id | email             |
++---------+-------------------+
+| 1       | alice@example.com |
+| 4       | david@domain.com  |
++---------+-------------------+
+</pre>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li><strong>alice@example.com</strong> is valid because it contains one <code>@</code>, alice&nbsp;is alphanumeric, and example.com&nbsp;starts with a letter and ends with .com.</li>
+	<li><strong>bob_at_example.com</strong> is invalid because it contains an underscore instead of an <code>@</code>.</li>
+	<li><strong>charlie@example.net</strong> is invalid because the domain does not end with <code>.com</code>.</li>
+	<li><strong>david@domain.com</strong> is valid because it meets all criteria.</li>
+	<li><strong>eve@invalid</strong> is invalid because the domain does not end with <code>.com</code>.</li>
+</ul>
+
+<p>Result table is ordered by user_id in ascending order.</p>
+</div>
+
+<!-- description:end -->
+
+## 解法
+
+<!-- solution:start -->
+
+### 方法一：正则表达式
+
+我们可以使用正则表达式，通过 `REGEXP` 来匹配符合条件的邮箱地址。
+
+<!-- tabs:start -->
+
+#### MySQL
+
+```sql
+# Write your MySQL query statement below
+SELECT user_id, email
+FROM Users
+WHERE email REGEXP '^[A-Za-z0-9_]+@[A-Za-z][A-Za-z0-9]*\\.com$'
+ORDER BY 1;
+```
+
+#### Pandas
+
+```python
+import pandas as pd
+
+
+def find_valid_emails(users: pd.DataFrame) -> pd.DataFrame:
+    email_pattern = r"^[A-Za-z0-9_]+@[A-Za-z][A-Za-z0-9]*\.com$"
+    valid_emails = users[users["email"].str.match(email_pattern)]
+    valid_emails = valid_emails.sort_values(by="user_id")
+    return valid_emails
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
+<!-- problem:end -->

solution/3400-3499/3436.Find Valid Emails/README_EN.md

@@ -0,0 +1,127 @@
+---
+comments: true
+difficulty: Easy
+edit_url: https://github.com/doocs/leetcode/edit/main/solution/3400-3499/3436.Find%20Valid%20Emails/README_EN.md
+tags:
+    - Database
+---
+
+<!-- problem:start -->
+
+# [3436. Find Valid Emails](https://leetcode.com/problems/find-valid-emails)
+
+[中文文档](/solution/3400-3499/3436.Find%20Valid%20Emails/README.md)
+
+## Description
+
+<!-- description:start -->
+
+<p>Table: <code>Users</code></p>
+
+<pre>
++-----------------+---------+
+| Column Name     | Type    |
++-----------------+---------+
+| user_id         | int     |
+| email           | varchar |
++-----------------+---------+
+(user_id) is the unique key for this table.
+Each row contains a user&#39;s unique ID and email address.
+</pre>
+
+<p>Write a solution to find all the <strong>valid email addresses</strong>. A valid email address meets the following criteria:</p>
+
+<ul>
+	<li>It contains exactly one <code>@</code> symbol.</li>
+	<li>The part before the <code>@</code> symbol contains only <strong>alphanumeric</strong> characters and <strong>underscores</strong>.</li>
+	<li>The part after the <code>@</code> symbol contains a domain name <strong>that starts with a letter</strong> and ends with <code>.com</code>.</li>
+</ul>
+
+<p>Return<em> the result table ordered by</em> <code>user_id</code> <em>in</em> <strong>ascending </strong><em>order</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong></p>
+
+<p>Users table:</p>
+
+<pre class="example-io">
++---------+---------------------+
+| user_id | email               |
++---------+---------------------+
+| 1       | alice@example.com   |
+| 2       | bob_at_example.com  |
+| 3       | charlie@example.net |
+| 4       | david@domain.com    |
+| 5       | eve@invalid         |
++---------+---------------------+
+</pre>
+
+<p><strong>Output:</strong></p>
+
+<pre class="example-io">
++---------+-------------------+
+| user_id | email             |
++---------+-------------------+
+| 1       | alice@example.com |
+| 4       | david@domain.com  |
++---------+-------------------+
+</pre>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li><strong>alice@example.com</strong> is valid because it contains one <code>@</code>, alice&nbsp;is alphanumeric, and example.com&nbsp;starts with a letter and ends with .com.</li>
+	<li><strong>bob_at_example.com</strong> is invalid because it contains an underscore instead of an <code>@</code>.</li>
+	<li><strong>charlie@example.net</strong> is invalid because the domain does not end with <code>.com</code>.</li>
+	<li><strong>david@domain.com</strong> is valid because it meets all criteria.</li>
+	<li><strong>eve@invalid</strong> is invalid because the domain does not end with <code>.com</code>.</li>
+</ul>
+
+<p>Result table is ordered by user_id in ascending order.</p>
+</div>
+
+<!-- description:end -->
+
+## Solutions
+
+<!-- solution:start -->
+
+### Solution 1: Regular Expression
+
+We can use a regular expression with `REGEXP` to match valid email addresses.
+
+The time complexity is $O(n)$, and the space complexity is $O(1)$. Here, $n$ is the length of the input string.
+
+<!-- tabs:start -->
+
+#### MySQL
+
+```sql
+# Write your MySQL query statement below
+SELECT user_id, email
+FROM Users
+WHERE email REGEXP '^[A-Za-z0-9_]+@[A-Za-z][A-Za-z0-9]*\\.com$'
+ORDER BY 1;
+```
+
+#### Pandas
+
+```python
+import pandas as pd
+
+
+def find_valid_emails(users: pd.DataFrame) -> pd.DataFrame:
+    email_pattern = r"^[A-Za-z0-9_]+@[A-Za-z][A-Za-z0-9]*\.com$"
+    valid_emails = users[users["email"].str.match(email_pattern)]
+    valid_emails = valid_emails.sort_values(by="user_id")
+    return valid_emails
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
+<!-- problem:end -->

solution/3400-3499/3436.Find Valid Emails/Solution.py

@@ -0,0 +1,8 @@
+import pandas as pd
+
+
+def find_valid_emails(users: pd.DataFrame) -> pd.DataFrame:
+    email_pattern = r"^[A-Za-z0-9_]+@[A-Za-z][A-Za-z0-9]*\.com$"
+    valid_emails = users[users["email"].str.match(email_pattern)]
+    valid_emails = valid_emails.sort_values(by="user_id")
+    return valid_emails

solution/3400-3499/3436.Find Valid Emails/Solution.sql

@@ -0,0 +1,5 @@
+# Write your MySQL query statement below
+SELECT user_id, email
+FROM Users
+WHERE email REGEXP '^[A-Za-z0-9_]+@[A-Za-z][A-Za-z0-9]*\\.com$'
+ORDER BY 1;

solution/DATABASE_README.md

@@ -308,6 +308,7 @@
 | 3401 | [Find Circular Gift Exchange Chains](/solution/3400-3499/3401.Find%20Circular%20Gift%20Exchange%20Chains/README.md)                                          | `数据库` | 困难 | 🔒   |
 | 3415 | [查找具有三个连续数字的产品](/solution/3400-3499/3415.Find%20Products%20with%20Three%20Consecutive%20Digits/README.md)                                       | `数据库` | 简单 | 🔒   |
 | 3421 | [查找进步的学生](/solution/3400-3499/3421.Find%20Students%20Who%20Improved/README.md)                                                                        | `数据库` | 中等 |      |
+| 3436 | [Find Valid Emails](/solution/3400-3499/3436.Find%20Valid%20Emails/README.md)                                                                                |          | 简单 |      |
 
 ## 版权
 

solution/DATABASE_README_EN.md

@@ -306,6 +306,7 @@ Press <kbd>Control</kbd> + <kbd>F</kbd>(or <kbd>Command</kbd> + <kbd>F</kbd> on
 | 3401 | [Find Circular Gift Exchange Chains](/solution/3400-3499/3401.Find%20Circular%20Gift%20Exchange%20Chains/README_EN.md)                                                                       | `Database` | Hard       | 🔒     |
 | 3415 | [Find Products with Three Consecutive Digits](/solution/3400-3499/3415.Find%20Products%20with%20Three%20Consecutive%20Digits/README_EN.md)                                                   | `Database` | Easy       | 🔒     |
 | 3421 | [Find Students Who Improved](/solution/3400-3499/3421.Find%20Students%20Who%20Improved/README_EN.md)                                                                                         | `Database` | Medium     |        |
+| 3436 | [Find Valid Emails](/solution/3400-3499/3436.Find%20Valid%20Emails/README_EN.md)                                                                                                             |            | Easy       |        |
 
 ## Copyright
 

solution/README.md

@@ -3446,6 +3446,7 @@
 |  3433  |  [统计用户被提及情况](/solution/3400-3499/3433.Count%20Mentions%20Per%20User/README.md)  |  `数组`,`数学`,`排序`,`模拟`  |  中等  |  第 434 场周赛  |
 |  3434  |  [子数组操作后的最大频率](/solution/3400-3499/3434.Maximum%20Frequency%20After%20Subarray%20Operation/README.md)  |  `贪心`,`数组`,`哈希表`,`动态规划`,`前缀和`  |  中等  |  第 434 场周赛  |
 |  3435  |  [最短公共超序列的字母出现频率](/solution/3400-3499/3435.Frequencies%20of%20Shortest%20Supersequences/README.md)  |  `位运算`,`图`,`拓扑排序`,`数组`,`字符串`,`枚举`  |  困难  |  第 434 场周赛  |
+|  3436  |  [Find Valid Emails](/solution/3400-3499/3436.Find%20Valid%20Emails/README.md)  |    |  简单  |    |
 
 ## 版权
 

solution/README_EN.md

@@ -3444,6 +3444,7 @@ Press <kbd>Control</kbd> + <kbd>F</kbd>(or <kbd>Command</kbd> + <kbd>F</kbd> on
 |  3433  |  [Count Mentions Per User](/solution/3400-3499/3433.Count%20Mentions%20Per%20User/README_EN.md)  |  `Array`,`Math`,`Sorting`,`Simulation`  |  Medium  |  Weekly Contest 434  |
 |  3434  |  [Maximum Frequency After Subarray Operation](/solution/3400-3499/3434.Maximum%20Frequency%20After%20Subarray%20Operation/README_EN.md)  |  `Greedy`,`Array`,`Hash Table`,`Dynamic Programming`,`Prefix Sum`  |  Medium  |  Weekly Contest 434  |
 |  3435  |  [Frequencies of Shortest Supersequences](/solution/3400-3499/3435.Frequencies%20of%20Shortest%20Supersequences/README_EN.md)  |  `Bit Manipulation`,`Graph`,`Topological Sort`,`Array`,`String`,`Enumeration`  |  Hard  |  Weekly Contest 434  |
+|  3436  |  [Find Valid Emails](/solution/3400-3499/3436.Find%20Valid%20Emails/README_EN.md)  |    |  Easy  |    |
 
 ## Copyright