The Number of Seniors and Juniors to Join the Company II - Solution & Explanation

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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) of types ('Senior', 'Junior').
Each row of this table indicates the id of a candidate, their monthly salary, and their experience.
The salary of each candidate is guaranteed to be unique.

A company wants to hire new employees. The budget of the company for the salaries is $70000. The company's criteria for hiring are:

Keep hiring the senior with the smallest salary until you cannot hire any more seniors.
Use the remaining budget to hire the junior with the smallest salary.
Keep hiring the junior with the smallest salary until you cannot hire any more juniors.

Write a solution to find the ids of seniors and juniors hired under the mentioned criteria.

Return the result table in any order.

The result format is in the following example.

Example 1:

Input:
Candidates table:
+-------------+------------+--------+
| employee_id | experience | salary |
+-------------+------------+--------+
| 1           | Junior     | 10000  |
| 9           | Junior     | 15000  |
| 2           | Senior     | 20000  |
| 11          | Senior     | 16000  |
| 13          | Senior     | 50000  |
| 4           | Junior     | 40000  |
+-------------+------------+--------+
Output: 
+-------------+
| employee_id |
+-------------+
| 11          |
| 2           |
| 1           |
| 9           |
+-------------+
Explanation: 
We can hire 2 seniors with IDs (11, 2). Since the budget is $70000 and the sum of their salaries is $36000, we still have $34000 but they are not enough to hire the senior candidate with ID 13.
We can hire 2 juniors with IDs (1, 9). Since the remaining budget is $34000 and the sum of their salaries is $25000, we still have $9000 but they are not enough to hire the junior candidate with ID 4.

Example 2:

Input:
Candidates table:
+-------------+------------+--------+
| employee_id | experience | salary |
+-------------+------------+--------+
| 1           | Junior     | 25000  |
| 9           | Junior     | 10000  |
| 2           | Senior     | 85000  |
| 11          | Senior     | 80000  |
| 13          | Senior     | 90000  |
| 4           | Junior     | 30000  |
+-------------+------------+--------+
Output: 
+-------------+
| employee_id |
+-------------+
| 9           |
| 1           |
| 4           |
+-------------+
Explanation: 
We cannot hire any seniors with the current budget as we need at least $80000 to hire one senior.
We can hire all three juniors with the remaining budget.

Approach Overview

Problem Overview: A company has a fixed hiring budget and a list of candidates with their experience level (Senior or Junior) and salary. Seniors must be hired first, but you still want to maximize the total number of hires. The task is to compute how many seniors and juniors can be hired without exceeding the total budget.

Approach 1: Salary Ordering with Window Functions (O(n log n) time, O(n) space)

The key observation: within each experience group you should always hire the cheapest candidates first. Sorting by salary ensures the company can hire the maximum possible number of employees under the budget. First filter all senior candidates, order them by salary, and compute a cumulative cost using a SQL window function like SUM(salary) OVER (ORDER BY salary). Keep only those whose cumulative salary does not exceed the budget. This determines how many seniors can be hired.

After hiring seniors, compute the remaining budget by subtracting the total senior salary from the original budget. Then apply the same idea to juniors: order junior candidates by salary and compute their cumulative salary with another window function. Select the rows whose running total stays within the remaining budget. The count of these rows gives the number of juniors hired.

This strategy works because hiring cheaper employees first always maximizes the count under a fixed budget. SQL window functions make the solution clean: they let you compute running totals without procedural loops. The database performs sorting and cumulative aggregation efficiently.

The approach mainly relies on sorting and cumulative aggregation, common techniques in database query optimization. Window functions such as SUM() OVER and conditional filtering are frequently used patterns in advanced SQL interview problems involving ranking, prefix sums, or budget allocation scenarios.

Recommended for interviews: The window-function solution is what most interviewers expect. It clearly shows you understand sorting strategies, greedy selection (cheapest first), and SQL analytical functions. A naive approach that manually aggregates rows or simulates iteration would be harder to maintain and less performant, while the window function approach expresses the logic directly in SQL.

Solution

Code

MySQL

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Detailed Complexity Analysis

Approach	Time	Space	When to Use
Window Function + Salary Sorting	O(n log n)	O(n)	Best general solution in SQL. Uses running totals to determine how many candidates fit within the budget.
Manual Aggregation with Subqueries	O(n log n)	O(n)	Alternative when window functions are unavailable. More verbose and harder to read.

Video Solution

Leetcode HARD 2010 - Number of Seniors & Juniors to Join 2 : Explained by Everyday Data Science • Everyday Data Science • 770 views views

Frequently Asked Questions

Is The Number of Seniors and Juniors to Join the Company II easy or hard?

The problem is classified as Hard because it requires combining greedy reasoning with advanced SQL features like window functions and cumulative sums. Understanding how ordering and running totals interact with a fixed budget is the main challenge.

The Number of Seniors and Juniors to Join the Company II Python/Java solution

This problem is designed for SQL rather than general-purpose languages. A Python or Java implementation would simulate the same logic by sorting candidates by salary, computing prefix sums, hiring seniors first, and then filling remaining budget with juniors.

How to solve The Number of Seniors and Juniors to Join the Company II in O(n)?

Achieving strict O(n) time is difficult in SQL because the optimal strategy requires sorting candidates by salary to maximize hires. Most database engines implement sorting in O(n log n). Using window functions with ORDER BY salary is the standard and most efficient practical solution.

What is the best approach for The Number of Seniors and Juniors to Join the Company II?

The best approach uses SQL window functions with salary ordering. Seniors are sorted by salary and a running total is calculated using SUM(salary) OVER (ORDER BY salary). Candidates are selected while the cumulative salary stays within the budget. After determining seniors, the same logic is applied to juniors with the remaining budget.

Is The Number of Seniors and Juniors to Join the Company II asked at Google/Amazon/Meta?

Database problems involving ranking, running totals, and hiring allocation appear frequently in SQL interviews at companies like Amazon, Google, and Meta. Variations of this problem test knowledge of window functions, cumulative sums, and greedy selection strategies in SQL queries.

What data structure is used in The Number of Seniors and Juniors to Join the Company II?

The solution relies on relational database operations rather than traditional data structures. Conceptually it uses sorting and prefix sums implemented through SQL window functions such as SUM() OVER. These provide running totals similar to prefix arrays in algorithmic problems.

What is the time complexity of The Number of Seniors and Juniors to Join the Company II?

The time complexity is O(n log n) because the database must sort candidates by salary before computing the cumulative totals. Window functions then scan the sorted data once. Space complexity is typically O(n) for intermediate query results depending on the execution plan.

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Problem Info

DifficultyHard

Acceptance63.2%

Approaches1

Reading time5 min

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