PROGRAMMEERVAARDIGHEDEN

Hash tables test for hiring

See how candidates build a working hash-based solution to a practical coding problem.

35 minuten
1 task
Intermediate
Coding tasks
Questions in Engels
Desktop only

Use this test free See the question formats

Het korte antwoord

The Coding: Hash Tables test is one 35-minute task for mid-level software engineers, developers, data engineers and data scientists who write production code. It measures whether a candidate can use a hash map or hash set to solve a practical problem, and write a working function in one of six supported languages.

Wat het meet

Writing correct code that uses hash maps and hash sets to solve a practical problem.

Hash Tables

Use hash maps and sets for tasks such as counting, grouping, fast lookup, deduplication or tracking state by key.

Question formats

Coding tasks

The candidate: Writes or fixes code in an editor and runs it against examples.

You see: Working code, checked against hidden test cases, not just knowledge of syntax.

1 task in 35 minutes.

Roles this test fits

Software engineers and developers at a mid level (backend, full-stack, mobile and game development), data engineers and data scientists who write production code, and technical roles where choosing the right data structure matters for speed.

What this coding task can show

Apply hash structures to a real problem
The task shows whether a candidate can use a map or set to count, group, look up, deduplicate or keep running state by key, rather than only describe the structure.
See choices that matter for speed
A hash map or hash set is the key to a correct and efficient answer, which matters when the role depends on picking the right data structure.
Ties and output order checked
Each task states its output order exactly, and the hidden cases include edge cases and ties, so you see whether the function gets the ordering details right.

What you get for each candidate

Example report (fictional data)Coding: Hash Tables

68%Percentile 40. Benchmark: HireValid candidates, n = 1.222

Hash Tables68%

Integrity ScoreHoge betrouwbaarheid

Stayed on the test tab throughout
No pasted answers
Answered at a steady pace

Scores, profiles and integrity signals are evidence for you to review alongside an interview, never an automatic decision.

Use this test free

How the test handles integrity signals

Each candidate receives a different question set, and the browser shows one question at a time. Code runs against hidden cases on HireValid’s servers; the cases and solutions do not reach the browser. The 35-minute timer runs on the server. Reloading restores the same question with only the remaining time, and candidates cannot go back. Pasting into the code editor is recorded. HireValid also records signals such as time away from the test tab and summarizes them in an Integrity Score with an evidence timeline. The employer reviews that evidence; the score never decides on its own. With candidate consent, the employer can add webcam photos at random moments.

Hoe we fraude met AI tegengaan · Integrity signals

Use the score as evidence

Review the score alongside a work sample and a structured interview, never on its own. A single task gives a narrower view than a longer test, and reliability is reported once 200 candidates have completed it. Compare the candidate’s reasoning with relevant evidence from your process, such as the Software Engineer test, Clean Code or Object Oriented Programming test.

Vragen voor gestructureerde sollicitatiegesprekken

Walk me through a production problem where you chose a map or set. How did you check the result?
Listen for the problem context, how the data was organized by key and how the candidate checked that the function behaved as intended.
How would you investigate a function that gives the wrong result for duplicate keys or tied outputs?
Listen for a clear debugging approach that considers edge cases and output order.
Describe a case where grouping records by key was useful in your work.
Listen for how the candidate connected the data structure to the task and checked the grouped results.

Understand scoring and benchmarks

Fairness and accommodations

Tasks use neutral, everyday scenarios with plain wording, names from many backgrounds and no money, sports or holiday references. Each task is written to the same standard in all six languages, states its inputs, outputs, limits and output order exactly, and avoids library features that only one language offers, so the choice of language does not change the difficulty.

You can give any candidate extra time as an accommodation. Results are evidence for a person to review, never an automatic decision.

Provisional: a single task gives a narrower view than a longer test, and reliability is reported once 200 candidates have completed it.

Lees hoe we met eerlijkheid omgaan

Test details

One programming task, solved in 35 minutes, where a hash map or hash set is the key to a correct and efficient answer: counting, grouping, fast lookup, deduplication or keeping running state by key. The candidate writes a working function in Python, JavaScript, Java, C#, C++ or Go, and the code runs against hidden test cases, including edge cases and ties.

Questions are in English.
Aids allowed: Scratch paper.
1 practice task, 10 minutes, before the timed test.
Taken on a desktop or laptop computer.

Python, JavaScript, Java, C#, C++, Go are trademarks of their owners. HireValid is not affiliated with or endorsed by them.

Veelgestelde vragen

What does the Coding: Hash Tables test measure?+

It measures writing correct code with hash maps and sets to solve a practical problem. The task may depend on counting, grouping, fast lookup, deduplication or keeping running state by key, with edge cases and ties included in hidden tests.

How does the Coding: Hash Tables test keep language choice fair?+

Tasks use neutral everyday scenarios, plain wording and names from many backgrounds. Each task states its inputs, outputs, limits and output order, follows the same standard in all six languages, and avoids library features available in only one language.

Can candidates use scratch paper on the Coding: Hash Tables test?+

Yes, scratch paper is allowed. The test needs a computer, and candidates write one working function in whichever of the six supported languages they know best.

Is there a practice set for the Coding: Hash Tables test?+

Yes. The practice set has one question and takes 10 minutes. It is separate from the scored task, which asks candidates to write a working function using a hash map or hash set.

Which roles and experience level suit the Coding: Hash Tables test?+

It is intended for mid-level software engineers and developers in backend, full-stack, mobile and game development, as well as data engineers and data scientists who write production code. It can also suit technical roles where choosing the right data structure matters for speed.