Leetcode #2988: Manager of the Largest Department
In this guide, we solve Leetcode #2988 Manager of the Largest Department in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
Table: Employees +-------------+---------+ | Column Name | Type | +-------------+---------+ | emp_id | int | | emp_name | varchar | | dep_id | int | | position | varchar | +-------------+---------+ emp_id is column of unique values for this table. This table contains emp_id, emp_name, dep_id, and position.
Quick Facts
- Difficulty: Medium
- Premium: Yes
- Tags: Database
Intuition
The task is relational in nature, which maps cleanly to DataFrame operations in Python.
By treating tables as DataFrames, joins and group-bys become concise and readable.
Approach
Load the inputs as DataFrames and apply the appropriate merge, filter, or group-by.
Select or rename the columns to match the required output.
Steps:
- Load inputs as DataFrames.
- Apply merge/groupby/filter operations.
- Select the output columns.
Example
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| emp_id | int |
| emp_name | varchar |
| dep_id | int |
| position | varchar |
+-------------+---------+
emp_id is column of unique values for this table.
This table contains emp_id, emp_name, dep_id, and position.
Python Solution
import duckdb
import pandas as pd
def solution(employees: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Employees", employees)
return con.execute("""WITH
T AS (
SELECT dep_id, COUNT(1) AS cnt
FROM Employees
GROUP BY 1
)
SELECT emp_name AS manager_name, t.dep_id
FROM
T AS t
JOIN Employees AS e ON t.dep_id = e.dep_id AND e.position = 'Manager'
WHERE cnt = (SELECT MAX(cnt) FROM T)
ORDER BY 2;""").df()
Complexity
The time complexity is O(n log n) (typical). The space complexity is O(n).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.