LeetCode 3421: Find Students Who Improved Solution

Master LeetCode problem 3421 (Find Students Who Improved), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

3421. Find Students Who Improved

Medium

Database

Problem Explanation

Explanation:

To solve this problem, we need to identify students who have shown improvement in their scores in the same subject on at least two different dates. We can achieve this by grouping the scores by student_id and subject, then filtering the groups to find students who meet the improvement criteria.

Group the scores by student_id and subject.
For each group, check if the student has taken exams on at least two different dates.
If the student has taken exams on at least two different dates, compare their first and latest scores.
If the latest score is higher than the first score, include the student in the result table.
Order the result table by student_id and subject in ascending order.

Time Complexity: O(n log n) - where n is the number of entries in the Scores table Space Complexity: O(n)

Solution Code

# Write your Java solution here
SELECT student_id, subject, MIN(score) as first_score, MAX(score) as latest_score
FROM Scores
GROUP BY student_id, subject
HAVING COUNT(DISTINCT exam_date) > 1 AND latest_score > first_score
ORDER BY student_id, subject;

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