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leetcode-cn/problem (English)/查找僵尸会话(English) [find-zombie-sessions].html Normal file
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<p>Table: <code>app_events</code></p>
<pre>
+------------------+----------+
| Column Name | Type |
+------------------+----------+
| event_id | int |
| user_id | int |
| event_timestamp | datetime |
| event_type | varchar |
| session_id | varchar |
| event_value | int |
+------------------+----------+
event_id is the unique identifier for this table.
event_type can be app_open, click, scroll, purchase, or app_close.
session_id groups events within the same user session.
event_value represents: for purchase - amount in dollars, for scroll - pixels scrolled, for others - NULL.
</pre>
<p>Write a solution to identify <strong>zombie sessions,&nbsp;</strong>sessions where users appear active but show abnormal behavior patterns. A session is considered a <strong>zombie session</strong> if it meets ALL the following criteria:</p>
<ul>
<li>The session duration is <strong>more than</strong> <code>30</code> minutes.</li>
<li>Has <strong>at least</strong> <code>5</code> scroll events.</li>
<li>The <strong>click-to-scroll ratio</strong> is less than <code>0.20</code> .</li>
<li><strong>No purchases</strong> were made during the session.</li>
</ul>
<p>Return <em>the result table ordered by</em>&nbsp;<code>scroll_count</code> <em>in <strong>descending</strong> order, then by</em> <code>session_id</code> <em>in <strong>ascending</strong> order</em>.</p>
<p>The result format is in the following example.</p>
<p>&nbsp;</p>
<p><strong class="example">Example:</strong></p>
<div class="example-block">
<p><strong>Input:</strong></p>
<p>app_events table:</p>
<pre class="example-io">
+----------+---------+---------------------+------------+------------+-------------+
| event_id | user_id | event_timestamp | event_type | session_id | event_value |
+----------+---------+---------------------+------------+------------+-------------+
| 1 | 201 | 2024-03-01 10:00:00 | app_open | S001 | NULL |
| 2 | 201 | 2024-03-01 10:05:00 | scroll | S001 | 500 |
| 3 | 201 | 2024-03-01 10:10:00 | scroll | S001 | 750 |
| 4 | 201 | 2024-03-01 10:15:00 | scroll | S001 | 600 |
| 5 | 201 | 2024-03-01 10:20:00 | scroll | S001 | 800 |
| 6 | 201 | 2024-03-01 10:25:00 | scroll | S001 | 550 |
| 7 | 201 | 2024-03-01 10:30:00 | scroll | S001 | 900 |
| 8 | 201 | 2024-03-01 10:35:00 | app_close | S001 | NULL |
| 9 | 202 | 2024-03-01 11:00:00 | app_open | S002 | NULL |
| 10 | 202 | 2024-03-01 11:02:00 | click | S002 | NULL |
| 11 | 202 | 2024-03-01 11:05:00 | scroll | S002 | 400 |
| 12 | 202 | 2024-03-01 11:08:00 | click | S002 | NULL |
| 13 | 202 | 2024-03-01 11:10:00 | scroll | S002 | 350 |
| 14 | 202 | 2024-03-01 11:15:00 | purchase | S002 | 50 |
| 15 | 202 | 2024-03-01 11:20:00 | app_close | S002 | NULL |
| 16 | 203 | 2024-03-01 12:00:00 | app_open | S003 | NULL |
| 17 | 203 | 2024-03-01 12:10:00 | scroll | S003 | 1000 |
| 18 | 203 | 2024-03-01 12:20:00 | scroll | S003 | 1200 |
| 19 | 203 | 2024-03-01 12:25:00 | click | S003 | NULL |
| 20 | 203 | 2024-03-01 12:30:00 | scroll | S003 | 800 |
| 21 | 203 | 2024-03-01 12:40:00 | scroll | S003 | 900 |
| 22 | 203 | 2024-03-01 12:50:00 | scroll | S003 | 1100 |
| 23 | 203 | 2024-03-01 13:00:00 | app_close | S003 | NULL |
| 24 | 204 | 2024-03-01 14:00:00 | app_open | S004 | NULL |
| 25 | 204 | 2024-03-01 14:05:00 | scroll | S004 | 600 |
| 26 | 204 | 2024-03-01 14:08:00 | scroll | S004 | 700 |
| 27 | 204 | 2024-03-01 14:10:00 | click | S004 | NULL |
| 28 | 204 | 2024-03-01 14:12:00 | app_close | S004 | NULL |
+----------+---------+---------------------+------------+------------+-------------+
</pre>
<p><strong>Output:</strong></p>
<pre class="example-io">
+------------+---------+--------------------------+--------------+
| session_id | user_id | session_duration_minutes | scroll_count |
+------------+---------+--------------------------+--------------+
| S001 | 201 | 35 | 6 |
+------------+---------+--------------------------+--------------+
</pre>
<p><strong>Explanation:</strong></p>
<ul>
<li><strong>Session S001 (User 201)</strong>:
<ul>
<li>Duration: 10:00:00 to 10:35:00 = 35 minutes (more than 30)&nbsp;</li>
<li>Scroll events: 6 (at least 5)&nbsp;</li>
<li>Click events: 0</li>
<li>Click-to-scroll ratio: 0/6 = 0.00 (less than 0.20)&nbsp;</li>
<li>Purchases: 0 (no purchases)&nbsp;</li>
<li>S001 is a zombie session (meets all criteria)</li>
</ul>
</li>
<li><strong>Session S002 (User 202)</strong>:
<ul>
<li>Duration: 11:00:00 to 11:20:00 = 20 minutes (less than 30)&nbsp;</li>
<li>Has a purchase event&nbsp;</li>
<li>S002 is&nbsp;not a zombie session&nbsp;</li>
</ul>
</li>
<li><strong>Session S003 (User 203)</strong>:
<ul>
<li>Duration: 12:00:00 to 13:00:00 = 60 minutes (more than 30)&nbsp;</li>
<li>Scroll events: 5 (at least 5)&nbsp;</li>
<li>Click events: 1</li>
<li>Click-to-scroll ratio: 1/5 = 0.20 (not less than 0.20)&nbsp;</li>
<li>Purchases: 0 (no purchases)&nbsp;</li>
<li>S003 is&nbsp;not a zombie session (click-to-scroll ratio equals 0.20, needs to be less)</li>
</ul>
</li>
<li><strong>Session S004 (User 204)</strong>:
<ul>
<li>Duration: 14:00:00 to 14:12:00 = 12 minutes (less than 30)&nbsp;</li>
<li>Scroll events: 2 (less than 5)&nbsp;</li>
<li>S004&nbsp; is not a zombie session&nbsp;</li>
</ul>
</li>
</ul>
<p>The result table is ordered by scroll_count in descending order, then by session_id in ascending order.</p>
</div>