Leetcode #2004: The Number of Seniors and Juniors to Join the Company
In this guide, we solve Leetcode #2004 The Number of Seniors and Juniors to Join the Company 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: Candidates +-------------+------+ | Column Name | Type | +-------------+------+ | employee_id | int | | experience | enum | | salary | int | +-------------+------+ employee_id is the column with unique values for this table. experience is an ENUM (category) type of values ('Senior', 'Junior').
Quick Facts
- Difficulty: Hard
- 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 |
+-------------+------+
| employee_id | int |
| experience | enum |
| salary | int |
+-------------+------+
employee_id is the column with unique values for this table.
experience is an ENUM (category) type of values ('Senior', 'Junior').
Each row of this table indicates the id of a candidate, their monthly salary, and their experience.
Python Solution
import duckdb
import pandas as pd
def solution(candidates: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Candidates", candidates)
return con.execute("""WITH
s AS (
SELECT
employee_id,
SUM(salary) OVER (ORDER BY salary) AS cur
FROM Candidates
WHERE experience = 'Senior'
),
j AS (
SELECT
employee_id,
IFNULL(
SELECT
MAX(cur)
FROM s
WHERE cur <= 70000,
0
) + SUM(salary) OVER (ORDER BY salary) AS cur
FROM Candidates
WHERE experience = 'Junior'
)
SELECT
'Senior' AS experience,
COUNT(employee_id) AS accepted_candidates
FROM s
WHERE cur <= 70000
UNION ALL
SELECT
'Junior' AS experience,
COUNT(employee_id) AS accepted_candidates
FROM j
WHERE cur <= 70000;""").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.