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2023-12-09 18:42:21 +08:00
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leetcode/problem/number-of-unique-subjects-taught-by-each-teacher.html Normal file
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<p>Table: <code>Teacher</code></p>
<pre>
+-------------+------+
| Column Name | Type |
+-------------+------+
| teacher_id | int |
| subject_id | int |
| dept_id | int |
+-------------+------+
(subject_id, dept_id) is the primary key (combinations of columns with unique values) of this table.
Each row in this table indicates that the teacher with teacher_id teaches the subject subject_id in the department dept_id.
</pre>
<p>&nbsp;</p>
<p>Write a solution to calculate&nbsp;the number of unique subjects each teacher teaches in the university.</p>
<p>Return the result table in <strong>any order</strong>.</p>
<p>The&nbsp;result format is shown in the following example.</p>
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre>
<strong>Input:</strong>
Teacher table:
+------------+------------+---------+
| teacher_id | subject_id | dept_id |
+------------+------------+---------+
| 1 | 2 | 3 |
| 1 | 2 | 4 |
| 1 | 3 | 3 |
| 2 | 1 | 1 |
| 2 | 2 | 1 |
| 2 | 3 | 1 |
| 2 | 4 | 1 |
+------------+------------+---------+
<strong>Output:</strong>
+------------+-----+
| teacher_id | cnt |
+------------+-----+
| 1 | 2 |
| 2 | 4 |
+------------+-----+
<strong>Explanation:</strong>
Teacher 1:
- They teach subject 2 in departments 3 and 4.
- They teach subject 3 in department 3.
Teacher 2:
- They teach subject 1 in department 1.
- They teach subject 2 in department 1.
- They teach subject 3 in department 1.
- They teach subject 4 in department 1.
</pre>