The student's solution demonstrates a good understanding of SQL queries and window functions. Here's a detailed evaluation:

1. Correctness:

   • Problem 1 (Rank Scores): Correctly uses DENSE_RANK() to solve the problem.
   • Problem 2 (Exchange Seats): Correctly handles both odd and even IDs, including the edge case for the last odd ID.
   • Problem 3 (Tree Node): Correctly identifies root, inner, and leaf nodes using CASE and subqueries.
   • Problem 4 (Department Top 3 Salaries): Correctly uses DENSE_RANK() with PARTITION BY to solve the problem.

2. Time Complexity:

   • All solutions appear to have optimal time complexity for their respective problems, typically O(n) or O(n log n) for sorting/ranking operations.

3. Space Complexity:

   • The solutions use reasonable space complexity, primarily for storing intermediate results during window function operations.

4. Code Quality:

   • The code is generally well-structured and readable.
   • Consistent indentation and formatting.
   • Good use of SQL keywords in uppercase.
   • Could improve by adding comments explaining the logic for each problem.

5. Efficiency:

   • All solutions appear efficient for their respective problems.
   • No obvious optimizations needed, though for Problem 4, an alternative approach using JOIN with a subquery might be worth considering for very large datasets.

Areas for improvement:

• Adding brief comments explaining the approach for each problem would enhance readability.
• The README.md file could be better organized with clear separation between problem descriptions and solutions.
• For Problem 3, the subquery could potentially be replaced with a LEFT JOIN for better readability.