How do you solve Department Highest Salary on LeetCode?

Department Highest Salary (LeetCode #184) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Using a HashMap allows efficient storage and retrieval of maximum salaries.

What is the brute force solution for Department Highest Salary?

The brute force approach for Department Highest Salary is Brute Force, with O(n²) time complexity and O(1) space complexity. In the brute force approach, we will check each employee's salary against all other employees in the same department to find the highest salary. This method is straightforward but inefficient. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Department Highest Salary?

Department Highest Salary uses the following concepts: Database. The recommended patterns to study are: Hash Map, Grouping, Aggregation.

What are the interview tips for Department Highest Salary?

Always clarify if you need to handle ties in salaries. Discuss your thought process and approach before jumping into coding. Practice writing SQL queries as they are common in technical interviews.

What are common mistakes when solving Department Highest Salary?

Not considering employees with the same highest salary. Overlooking the need to join with the Department table for final output.

#184

Department Highest Salary

Medium

DatabaseHash MapGroupingAggregation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

The optimal solution uses a single pass through the Employee table to find the highest salary for each department using a HashMap. This reduces the number of comparisons significantly.

⚙️

Algorithm

3 steps

1Step 1: Initialize a HashMap to store the highest salary and corresponding employee for each department.
2Step 2: Iterate through the Employee table, updating the HashMap with the employee details if their salary is higher than the current stored salary for that department.
3Step 3: Extract the results from the HashMap to get the final output.

solution.py7 lines

1SELECT departmentId AS Department, name AS Employee, salary AS Salary
2FROM Employee
3WHERE (departmentId, salary) IN (
4    SELECT departmentId, MAX(salary)
5    FROM Employee
6    GROUP BY departmentId
7);

ℹ

Complexity note: This complexity is linear because we only pass through the Employee table once to build the HashMap, and then we perform a single query to get the results.

1Using a HashMap allows efficient storage and retrieval of maximum salaries.
2Grouping by department reduces the need for nested loops.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.