Added task 3586

src/main/java/g3501_3600/s3586_find_covid_recovery_patients/readme.md

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+3586\. Find COVID Recovery Patients
+
+Medium
+
+Table: `patients`
+
+    +-------------+---------+
+    | Column Name | Type    |
+    +-------------+---------+
+    | patient_id  | int     |
+    | patient_name| varchar |
+    | age         | int     |
+    +-------------+---------+
+    patient_id is the unique identifier for this table.
+    Each row contains information about a patient.
+
+Table: `covid_tests`
+
+    +-------------+---------+
+    | Column Name | Type    |
+    +-------------+---------+
+    | test_id     | int     |
+    | patient_id  | int     |
+    | test_date   | date    |
+    | result      | varchar |
+    +-------------+---------+
+    test_id is the unique identifier for this table.
+    Each row represents a COVID test result. The result can be Positive, Negative, or Inconclusive. 
+
+Write a solution to find patients who have **recovered from COVID** - patients who tested positive but later tested negative.
+
+*   A patient is considered recovered if they have **at least one** **Positive** test followed by at least one **Negative** test on a **later date**
+*   Calculate the **recovery time** in days as the **difference** between the **first positive test** and the **first negative test** after that **positive test**
+*   **Only include** patients who have both positive and negative test results
+
+Return _the result table ordered by_ `recovery_time` _in **ascending** order, then by_ `patient_name` _in **ascending** order_.
+
+The result format is in the following example.
+
+**Example:**
+
+**Input:**
+
+patients table:
+
+    +------------+--------------+-----+
+    | patient_id | patient_name | age |
+    +------------+--------------+-----+
+    | 1          | Alice Smith  | 28  |
+    | 2          | Bob Johnson  | 35  |
+    | 3          | Carol Davis  | 42  |
+    | 4          | David Wilson | 31  |
+    | 5          | Emma Brown   | 29  |
+    +------------+--------------+-----+ 
+
+covid\_tests table:
+
+    +---------+------------+------------+--------------+
+    | test_id | patient_id | test_date  | result       |
+    |---------|------------|------------|--------------|
+    | 1       | 1          | 2023-01-15 | Positive     |
+    | 2       | 1          | 2023-01-25 | Negative     |
+    | 3       | 2          | 2023-02-01 | Positive     |
+    | 4       | 2          | 2023-02-05 | Inconclusive |
+    | 5       | 2          | 2023-02-12 | Negative     |
+    | 6       | 3          | 2023-01-20 | Negative     |
+    | 7       | 3          | 2023-02-10 | Positive     |
+    | 8       | 3          | 2023-02-20 | Negative     |
+    | 9       | 4          | 2023-01-10 | Positive     |
+    | 10      | 4          | 2023-01-18 | Positive     |
+    | 11      | 5          | 2023-02-15 | Negative     |
+    | 12      | 5          | 2023-02-20 | Negative     |
+    +---------+------------+------------+--------------+
+
+**Output:**
+
+    +------------+--------------+-----+---------------+
+    | patient_id | patient_name | age | recovery_time |
+    |------------|--------------|-----|---------------|
+    | 1          | Alice Smith  | 28  | 10            |
+    | 3          | Carol Davis  | 42  | 10            |
+    | 2          | Bob Johnson  | 35  | 11            |
+    +------------+--------------+-----+---------------+
+
+**Explanation:**
+
+*   **Alice Smith (patient\_id = 1):**
+    *   First positive test: 2023-01-15
+    *   First negative test after positive: 2023-01-25
+    *   Recovery time: 25 - 15 = 10 days
+*   **Bob Johnson (patient\_id = 2):**
+    *   First positive test: 2023-02-01
+    *   Inconclusive test on 2023-02-05 (ignored for recovery calculation)
+    *   First negative test after positive: 2023-02-12
+    *   Recovery time: 12 - 1 = 11 days
+*   **Carol Davis (patient\_id = 3):**
+    *   Had negative test on 2023-01-20 (before positive test)
+    *   First positive test: 2023-02-10
+    *   First negative test after positive: 2023-02-20
+    *   Recovery time: 20 - 10 = 10 days
+*   **Patients not included:**
+    *   David Wilson (patient\_id = 4): Only has positive tests, no negative test after positive
+    *   Emma Brown (patient\_id = 5): Only has negative tests, never tested positive
+
+Output table is ordered by recovery\_time in ascending order, and then by patient\_name in ascending order.

src/main/java/g3501_3600/s3586_find_covid_recovery_patients/script.sql

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+# Write your MySQL query statement below
+# #Medium #Database #2025_06_19_Time_471_ms_(97.17%)_Space_0.0_MB_(100.00%)
+-- mysql
+-- SELECT 
+--     p.patient_id,
+--     p.patient_name,
+--     p.age,
+--     DATEDIFF(
+--         min(neg.test_date),
+--         min(pos.test_date)
+--     ) AS recovery_time
+-- FROM 
+--     patients p
+--     JOIN covid_tests pos ON
+--         p.patient_id = pos.patient_id AND pos.result = 'Positive'
+--     JOIN covid_tests neg ON 
+--         p.patient_id = neg.patient_id AND neg.result = 'Negative'
+-- WHERE 
+--     neg.test_date > pos.test_date
+-- GROUP BY 
+--     p.patient_id, p.patient_name, p.age
+-- ORDER BY 
+--     recovery_time, p.patient_name;
+select 
+    p.patient_id,
+    p.patient_name,
+    p.age,
+    datediff(
+        day, 
+        pos.first_pos_date, 
+        neg.first_neg_date
+    ) as recovery_time
+from 
+    patients p
+    join (
+        select patient_id, min(test_date) as first_pos_date 
+        from covid_tests 
+        where result = 'Positive'
+        group by patient_id
+    ) pos on p.patient_id = pos.patient_id
+    join (
+        select 
+            c1.patient_id, 
+            min(c1.test_date) as first_neg_date
+        from 
+            covid_tests c1
+            join (
+                select patient_id, min(test_date) as first_pos_date 
+                from covid_tests 
+                where result = 'Positive'
+                group by patient_id
+            ) p2 on c1.patient_id = p2.patient_id
+        where 
+            c1.result = 'Negative'
+            and c1.test_date > p2.first_pos_date
+        group by c1.patient_id
+    ) neg on p.patient_id = neg.patient_id
+order by 
+    recovery_time ASC, p.patient_name ASC;

src/test/java/g3501_3600/s3586_find_covid_recovery_patients/MysqlTest.java

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+package g3501_3600.s3586_find_covid_recovery_patients;
+
+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 patients (patient_id INTEGER, patient_name VARCHAR(255), age INTEGER); "
+                        + "INSERT INTO patients (patient_id, patient_name, age) VALUES"
+                        + "(1, 'Alice Smith', 28),"
+                        + "(2, 'Bob Johnson', 35),"
+                        + "(3, 'Carol Davis', 42),"
+                        + "(4, 'David Wilson', 31),"
+                        + "(5, 'Emma Brown', 29);"
+                        + "CREATE TABLE covid_tests (test_id INTEGER, patient_id INTEGER"
+                        + ", test_date DATE, result VARCHAR(255)); "
+                        + "INSERT INTO covid_tests (test_id, patient_id, test_date, result) VALUES"
+                        + "(1, 1, '2023-01-15', 'Positive'),"
+                        + "(2, 1, '2023-01-25', 'Negative'),"
+                        + "(3, 2, '2023-02-01', 'Positive'),"
+                        + "(4, 2, '2023-02-05', 'Inconclusive'),"
+                        + "(5, 2, '2023-02-12', 'Negative'),"
+                        + "(6, 3, '2023-01-20', 'Negative'),"
+                        + "(7, 3, '2023-02-10', 'Positive'),"
+                        + "(8, 3, '2023-02-20', 'Negative'),"
+                        + "(9, 4, '2023-01-10', 'Positive'),"
+                        + "(10, 4, '2023-01-18', 'Positive'),"
+                        + "(11, 5, '2023-02-15', 'Negative'),"
+                        + "(12, 5, '2023-02-20', 'Negative');")
+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/g3501_3600/"
+                                                                    + "s3586_find_covid_recovery_patients/"
+                                                                    + "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("Alice Smith"));
+                assertThat(resultSet.getNString(3), equalTo("28"));
+                assertThat(resultSet.getNString(4), equalTo("10"));
+                assertThat(resultSet.next(), equalTo(true));
+                assertThat(resultSet.getNString(1), equalTo("3"));
+                assertThat(resultSet.getNString(2), equalTo("Carol Davis"));
+                assertThat(resultSet.getNString(3), equalTo("42"));
+                assertThat(resultSet.getNString(4), equalTo("10"));
+                assertThat(resultSet.next(), equalTo(true));
+                assertThat(resultSet.getNString(1), equalTo("2"));
+                assertThat(resultSet.getNString(2), equalTo("Bob Johnson"));
+                assertThat(resultSet.getNString(3), equalTo("35"));
+                assertThat(resultSet.getNString(4), equalTo("11"));
+                assertThat(resultSet.next(), equalTo(false));
+            }
+        }
+    }
+}