Added task 3642

gradlew

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 #
-# Copyright © 2015-2021 the original authors.
+# Copyright © 2015 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.

src/main/java/g3601_3700/s3642_find_books_with_polarized_opinions/readme.md

@@ -0,0 +1,118 @@
+3642\. Find Books with Polarized Opinions
+
+Easy
+
+Table: `books`
+
+    +-------------+---------+
+    | 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.
+
+Table: `reading_sessions`
+
+    +----------------+---------+
+    | 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.
+
+Write a solution to find books that have **polarized opinions** - books that receive both very high ratings and very low ratings from different readers.
+
+*   A book has polarized opinions if it has `at least one rating ≥ 4` and `at least one rating ≤ 2`
+*   Only consider books that have **at least** `5` **reading sessions**
+*   Calculate the **rating spread** as (`highest_rating - lowest_rating`)
+*   Calculate the **polarization score** as the number of extreme ratings (`ratings ≤ 2 or ≥ 4`) divided by total sessions
+*   **Only include** books where `polarization score ≥ 0.6` (at least `60%` extreme ratings)
+
+Return _the result table ordered by polarization score in **descending** order, then by title in **descending** order_.
+
+The result format is in the following example.
+
+**Example:**
+
+**Input:**
+
+books table:
+
+    +---------+------------------------+---------------+----------+-------+
+    | 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   |
+    +---------+------------------------+---------------+----------+-------+
+
+reading\_sessions table:
+
+    +------------+---------+-------------+------------+----------------+
+    | 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              |
+    +------------+---------+-------------+------------+----------------+
+
+**Output:**
+
+    +---------+------------------+---------------+-----------+-------+---------------+--------------------+
+    | 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               |
+    +---------+------------------+---------------+-----------+-------+---------------+--------------------+
+
+**Explanation:**
+
+*   **The Great Gatsby (book\_id = 1):**
+    *   Has 5 reading sessions (meets minimum requirement)
+    *   Ratings: 5, 1, 4, 2, 5
+    *   Has ratings ≥ 4: 5, 4, 5 (3 sessions)
+    *   Has ratings ≤ 2: 1, 2 (2 sessions)
+    *   Rating spread: 5 - 1 = 4
+    *   Extreme ratings (≤2 or ≥4): All 5 sessions (5, 1, 4, 2, 5)
+    *   Polarization score: 5/5 = 1.00 (≥ 0.6, qualifies)
+*   **1984 (book\_id = 3):**
+    *   Has 6 reading sessions (meets minimum requirement)
+    *   Ratings: 2, 1, 2, 1, 4, 5
+    *   Has ratings ≥ 4: 4, 5 (2 sessions)
+    *   Has ratings ≤ 2: 2, 1, 2, 1 (4 sessions)
+    *   Rating spread: 5 - 1 = 4
+    *   Extreme ratings (≤2 or ≥4): All 6 sessions (2, 1, 2, 1, 4, 5)
+    *   Polarization score: 6/6 = 1.00 (≥ 0.6, qualifies)
+*   **Books not included:**
+    *   To Kill a Mockingbird (book\_id = 2): All ratings are 4-5, no low ratings (≤2)
+    *   Pride and Prejudice (book\_id = 4): Only 2 sessions (< 5 minimum)
+    *   The Catcher in the Rye (book\_id = 5): Only 2 sessions (< 5 minimum)
+
+The result table is ordered by polarization score in descending order, then by book title in descending order.

src/main/java/g3601_3700/s3642_find_books_with_polarized_opinions/script.sql

@@ -0,0 +1,30 @@
+# Write your MySQL query statement below
+# #Easy #Database #2025_08_10_Time_490_ms_(100.00%)_Space_0.0_MB_(100.00%)
+WITH book_stats AS (
+    SELECT
+        book_id,
+        COUNT(*) AS total_sessions,
+        SUM(CASE WHEN session_rating <> 3 THEN 1 ELSE 0 END) AS extreme_ratings,
+        MAX(session_rating) AS max_rating,
+        MIN(session_rating) AS min_rating,
+        SUM(CASE WHEN session_rating > 3 THEN 1 ELSE 0 END) AS high_ratings,
+        SUM(CASE WHEN session_rating <= 2 THEN 1 ELSE 0 END) AS low_ratings
+    FROM reading_sessions
+    GROUP BY book_id
+)
+SELECT
+    bs.book_id,
+    b.title,
+    b.author,
+    b.genre,
+    b.pages,
+    (bs.max_rating - bs.min_rating) AS rating_spread,
+    ROUND(bs.extreme_ratings * 1.0 / bs.total_sessions, 2) AS polarization_score
+FROM book_stats bs
+JOIN books b USING (book_id)
+WHERE 
+    bs.total_sessions >= 5
+    AND bs.high_ratings > 0
+    AND bs.low_ratings > 0
+    AND (bs.extreme_ratings * 1.0 / bs.total_sessions) >= 0.6
+ORDER BY polarization_score DESC, b.title DESC;

src/test/java/g3601_3700/s3642_find_books_with_polarized_opinions/MysqlTest.java

@@ -0,0 +1,103 @@
+package g3601_3700.s3642_find_books_with_polarized_opinions;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.stream.Collectors;
+import javax.sql.DataSource;
+import org.junit.jupiter.api.Test;
+import org.zapodot.junit.db.annotations.EmbeddedDatabase;
+import org.zapodot.junit.db.annotations.EmbeddedDatabaseTest;
+import org.zapodot.junit.db.common.CompatibilityMode;
+
+@EmbeddedDatabaseTest(
+        compatibilityMode = CompatibilityMode.MySQL,
+        initialSqls =
+                "CREATE TABLE books ("
+                        + "    book_id INT PRIMARY KEY,"
+                        + "    title VARCHAR(255),"
+                        + "    author VARCHAR(255),"
+                        + "    genre VARCHAR(50),"
+                        + "    pages INT"
+                        + ");"
+                        + "INSERT INTO books (book_id, title, author, genre, pages) VALUES"
+                        + "(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);"
+                        + "CREATE TABLE reading_sessions ("
+                        + "    session_id INT PRIMARY KEY,"
+                        + "    book_id INT,"
+                        + "    reader_name VARCHAR(100),"
+                        + "    pages_read INT,"
+                        + "    session_rating INT,"
+                        + "    FOREIGN KEY (book_id) REFERENCES books(book_id)"
+                        + ");"
+                        + "INSERT INTO reading_sessions (session_id, book_id, "
+                        + "reader_name, pages_read, session_rating) VALUES"
+                        + "(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);")
+class MysqlTest {
+    @Test
+    void testScript(@EmbeddedDatabase DataSource dataSource)
+            throws SQLException, FileNotFoundException {
+        try (final Connection connection = dataSource.getConnection()) {
+            try (final Statement statement = connection.createStatement();
+                    final ResultSet resultSet =
+                            statement.executeQuery(
+                                    new BufferedReader(
+                                                    new FileReader(
+                                                            "src/main/java/g3601_3700/"
+                                                                    + "s3642_find_books_with_"
+                                                                    + "polarized_opinions/"
+                                                                    + "script.sql"))
+                                            .lines()
+                                            .collect(Collectors.joining("\n"))
+                                            .replaceAll("#.*?\\r?\\n", ""))) {
+                assertThat(resultSet.next(), equalTo(true));
+                assertThat(resultSet.getNString(1), equalTo("1"));
+                assertThat(resultSet.getNString(2), equalTo("The Great Gatsby"));
+                assertThat(resultSet.getNString(3), equalTo("F. Scott"));
+                assertThat(resultSet.getNString(4), equalTo("Fiction"));
+                assertThat(resultSet.getNString(5), equalTo("180"));
+                assertThat(resultSet.getNString(6), equalTo("4"));
+                assertThat(resultSet.getNString(7), equalTo("1.00"));
+                assertThat(resultSet.next(), equalTo(true));
+                assertThat(resultSet.getNString(1), equalTo("3"));
+                assertThat(resultSet.getNString(2), equalTo("1984"));
+                assertThat(resultSet.getNString(3), equalTo("George Orwell"));
+                assertThat(resultSet.getNString(4), equalTo("Dystopian"));
+                assertThat(resultSet.getNString(5), equalTo("328"));
+                assertThat(resultSet.getNString(6), equalTo("4"));
+                assertThat(resultSet.getNString(7), equalTo("1.00"));
+                assertThat(resultSet.next(), equalTo(false));
+            }
+        }
+    }
+}