L2 · Working engineerObject-oriented Python~8 min · 4 tests#79

Employee Management System Class

Design an EmployeeManager class with add, get, remove and average salary backed by a dict for O(1) lookups. Practical OOP design, tested in Python.

The problem

Implement EmployeeManager:

add_employee(name, salary) — add or update
get_employee(name) — return the salary, or None
remove_employee(name) — return True if removed, False if absent
average_salary() — average of all salaries, 0 if there are none

Examples

Example 1

Input

run_ops(EmployeeManager, [], [["add_employee", "John", 50000], ["add_employee", "Alice", 70000], ["get_employee", "John"]])

Expected output

[None, None, 50000]

Example 2

Input

run_ops(EmployeeManager, [], [["add_employee", "A", 100], ["add_employee", "B", 300], ["average_salary"]])

Expected output

[None, None, 200.0]

+ 2 hidden tests on Submit.

Edge cases to ask about

Empty manager
Removing a missing employee
Updating an existing employee

Hints

0/3

How an interviewer scores this

0/9

1. Understand the problemRestate it, ask about edge cases and input size.
2. Write a brute-force solutionCorrect first, clever later.
3. Get the correct outputautoAll visible examples pass.
4. Analyse time complexityautoCommit to a Big-O in the Complexity Lab.
5. Analyse space complexityautoExtra memory, not the input.
6. Identify the bottleneckautoMeasure your code — where does it bend?
7. OptimiseUsually: a set or dict instead of a scan.
8. Explain why it worksSay it out loud to Solvi.
9. Test the edge casesautoSubmit passes every hidden test.

Python 3.13 · EmployeeManager

class EmployeeManager:
    def __init__(self):
        pass

    def add_employee(self, name, salary):
        pass

    def get_employee(self, name):
        pass

    def remove_employee(self, name):
        pass

    def average_salary(self):
        pass

⌘/Ctrl + Enter runs the examples

Your code runs in real CPython inside your browser — nothing is sent anywhere. The first run downloads the interpreter (about 6 MB, once). Your code is saved on this device as you type.

Complexity Lab

What does this cost as n grows?

Interviewers score the analysis as much as the code. Commit to an answer first — then check it, and read why.

Time complexity of the optimal solution

Space complexity (extra memory)

Pick both to reveal the answer.

From brute force to optimal

The progression an interviewer wants to hear, one step at a time.

Approach	Time	Space	Idea
Dict keyed by name	O(1) per lookup, O(n) average	O(n)	Keep a running total to make average O(1).

Walkthrough of the optimal approach (try it yourself first)

A dict gives O(1) add, get and remove. average_salary is O(n) as written; if it is called often, keep a running total updated on add/remove to make it O(1) — a classic design trade-off to mention.

Complexity: O(1) time, O(n) space. Add/get/remove are O(1) dict operations; average is O(n) unless you maintain a running total.

Reveal the reference solution

class EmployeeManager:
    def __init__(self):
        self._salaries = {}

    def add_employee(self, name, salary):
        self._salaries[name] = salary

    def get_employee(self, name):
        return self._salaries.get(name)

    def remove_employee(self, name):
        return self._salaries.pop(name, None) is not None

    def average_salary(self):
        if not self._salaries:
            return 0
        return sum(self._salaries.values()) / len(self._salaries)

Follow-ups interviewers ask

Make average O(1).
Return the top 3 earners efficiently.

Frequently asked interview questions

Core interview concepts, complexities, and follow-ups scored by hiring teams.

What is the time complexity of Employee Management System Class in Python?

The optimal solution runs in O(1) time and O(n) auxiliary space. Add/get/remove are O(1) dict operations; average is O(n) unless you maintain a running total.

What follow-up questions do interviewers ask about Employee Management System Class?

Make average O(1). Return the top 3 earners efficiently.