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leetcode-cn/problem (English)/查找有两极分化观点的书籍(English) [find-books-with-polarized-opinions].html Normal file
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<p>Table: <code>books</code></p>
<pre>
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| book_id | int |
| title | varchar |
| author | varchar |
| genre | varchar |
| pages | int |
+-------------+---------+
book_id is the unique ID for this table.
Each row contains information about a book including its genre and page count.
</pre>
<p>Table: <code>reading_sessions</code></p>
<pre>
+----------------+---------+
| Column Name | Type |
+----------------+---------+
| session_id | int |
| book_id | int |
| reader_name | varchar |
| pages_read | int |
| session_rating | int |
+----------------+---------+
session_id is the unique ID for this table.
Each row represents a reading session where someone read a portion of a book. session_rating is on a scale of 1-5.
</pre>
<p>Write a solution to find books that have <strong>polarized opinions</strong> - books that receive both very high ratings and very low ratings from different readers.</p>
<ul>
<li>A book has polarized opinions if it has <code>at least one rating &ge; 4</code> and <code>at least one rating &le; 2</code></li>
<li>Only consider books that have <strong>at least </strong><code>5</code><strong> reading sessions</strong></li>
<li>Calculate the <strong>rating spread</strong> as (<code>highest_rating - lowest_rating</code>)</li>
<li>Calculate the <strong>polarization score</strong> as the number of extreme ratings (<code>ratings &le; 2 or &ge; 4</code>) divided by total sessions</li>
<li><strong>Only include</strong> books where <code>polarization score &ge; 0.6</code> (at least <code>60%</code> extreme ratings)</li>
</ul>
<p>Return <em>the result table ordered by polarization score in <strong>descending</strong> order, then by title in <strong>descending</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>books table:</p>
<pre class="example-io">
+---------+------------------------+---------------+----------+-------+
| book_id | title | author | genre | pages |
+---------+------------------------+---------------+----------+-------+
| 1 | The Great Gatsby | F. Scott | Fiction | 180 |
| 2 | To Kill a Mockingbird | Harper Lee | Fiction | 281 |
| 3 | 1984 | George Orwell | Dystopian| 328 |
| 4 | Pride and Prejudice | Jane Austen | Romance | 432 |
| 5 | The Catcher in the Rye | J.D. Salinger | Fiction | 277 |
+---------+------------------------+---------------+----------+-------+
</pre>
<p>reading_sessions table:</p>
<pre class="example-io">
+------------+---------+-------------+------------+----------------+
| session_id | book_id | reader_name | pages_read | session_rating |
+------------+---------+-------------+------------+----------------+
| 1 | 1 | Alice | 50 | 5 |
| 2 | 1 | Bob | 60 | 1 |
| 3 | 1 | Carol | 40 | 4 |
| 4 | 1 | David | 30 | 2 |
| 5 | 1 | Emma | 45 | 5 |
| 6 | 2 | Frank | 80 | 4 |
| 7 | 2 | Grace | 70 | 4 |
| 8 | 2 | Henry | 90 | 5 |
| 9 | 2 | Ivy | 60 | 4 |
| 10 | 2 | Jack | 75 | 4 |
| 11 | 3 | Kate | 100 | 2 |
| 12 | 3 | Liam | 120 | 1 |
| 13 | 3 | Mia | 80 | 2 |
| 14 | 3 | Noah | 90 | 1 |
| 15 | 3 | Olivia | 110 | 4 |
| 16 | 3 | Paul | 95 | 5 |
| 17 | 4 | Quinn | 150 | 3 |
| 18 | 4 | Ruby | 140 | 3 |
| 19 | 5 | Sam | 80 | 1 |
| 20 | 5 | Tara | 70 | 2 |
+------------+---------+-------------+------------+----------------+
</pre>
<p><strong>Output:</strong></p>
<pre class="example-io">
+---------+------------------+---------------+-----------+-------+---------------+--------------------+
| book_id | title | author | genre | pages | rating_spread | polarization_score |
+---------+------------------+---------------+-----------+-------+---------------+--------------------+
| 1 | The Great Gatsby | F. Scott | Fiction | 180 | 4 | 1.00 |
| 3 | 1984 | George Orwell | Dystopian | 328 | 4 | 1.00 |
+---------+------------------+---------------+-----------+-------+---------------+--------------------+
</pre>
<p><strong>Explanation:</strong></p>
<ul>
<li><strong>The Great Gatsby (book_id = 1):</strong>
<ul>
<li>Has 5 reading sessions (meets minimum requirement)</li>
<li>Ratings: 5, 1, 4, 2, 5</li>
<li>Has ratings &ge; 4: 5, 4, 5 (3 sessions)</li>
<li>Has ratings &le; 2: 1, 2 (2 sessions)</li>
<li>Rating spread: 5 - 1 = 4</li>
<li>Extreme ratings (&le;2 or &ge;4): All 5 sessions (5, 1, 4, 2, 5)</li>
<li>Polarization score: 5/5 = 1.00 (&ge; 0.6, qualifies)</li>
</ul>
</li>
<li><strong>1984 (book_id = 3):</strong>
<ul>
<li>Has 6 reading sessions (meets minimum requirement)</li>
<li>Ratings: 2, 1, 2, 1, 4, 5</li>
<li>Has ratings &ge; 4: 4, 5 (2 sessions)</li>
<li>Has ratings &le; 2: 2, 1, 2, 1 (4 sessions)</li>
<li>Rating spread: 5 - 1 = 4</li>
<li>Extreme ratings (&le;2 or &ge;4): All 6 sessions (2, 1, 2, 1, 4, 5)</li>
<li>Polarization score: 6/6 = 1.00 (&ge; 0.6, qualifies)</li>
</ul>
</li>
<li><strong>Books not included:</strong>
<ul>
<li>To Kill a Mockingbird (book_id = 2): All ratings are 4-5, no low ratings (&le;2)</li>
<li>Pride and Prejudice (book_id = 4): Only 2 sessions (&lt; 5 minimum)</li>
<li>The Catcher in the Rye (book_id = 5): Only 2 sessions (&lt; 5 minimum)</li>
</ul>
</li>
</ul>
<p>The result table is ordered by polarization score in descending order, then by book title in descending order.</p>
</div>