I recently completed the Virtu Trading HackerRank Online Assessment, and overall it was more straightforward than I expected. The assessment consisted of five coding questions with a total time limit of 75 minutes. I finished all five problems in about 40–45 minutes, passed every test case on my first submission, and spent the remaining time reviewing edge cases and cleaning up my code.
Although the overall difficulty wasn't particularly high, Virtu clearly values coding speed, implementation quality, and attention to detail. Most questions focused on fundamental algorithms rather than advanced data structures, making it important to write clean and bug-free code under time pressure.
OA Overview
- Platform: HackerRank
- Duration: 75 Minutes
- Questions: 5 Coding Problems
- Difficulty: Easy to Medium
- Main Topics: Strings, Greedy, Simulation, Arrays, Basic Mathematics
Unlike some quantitative trading companies that heavily emphasize advanced algorithms, Virtu's OA leaned more toward practical implementation. There were no graph algorithms, dynamic programming, or complicated data structures. Instead, the assessment rewarded candidates who could quickly understand the problem, implement a correct solution, and carefully handle boundary conditions.
Question 1 — Count Uniform Character Substrings
The first problem asked for the total number of contiguous substrings consisting entirely of identical characters.
The key observation is that if a consecutive block has length n, then it contributes n × (n + 1) / 2 valid substrings. The solution simply scans the string once, tracks the current run length, and adds the contribution whenever the character changes.
This is a classic linear scan problem with an overall time complexity of O(n) and constant extra space.
Question 2 — HexSpeak
The second problem involved converting a decimal number into a hexadecimal representation and then replacing specific digits according to the HexSpeak rules.
After converting the number into uppercase hexadecimal format:
- Replace 0 with O
- Replace 1 with I
The resulting string must contain only the characters A, B, C, D, E, I, and O. Otherwise, the answer should be ERROR.
This was mainly a straightforward simulation problem involving string manipulation and character validation.
Question 3 — Minimum Steps to a Fibonacci Number
The third question asked for the minimum number of increment or decrement operations required to transform an integer into the nearest Fibonacci number.
Since the maximum input value is only one million, generating every Fibonacci number up to that limit is trivial. After preprocessing the sequence, simply compute the absolute difference between the input value and every Fibonacci number, then return the minimum difference.
The algorithm is extremely efficient because there are only a few dozen Fibonacci numbers within the given range.
Question 4 — Apple Packing
This was a standard greedy problem.
The first element of the input represented the weight already inside the box, while the remaining elements represented the weights of individual apples. The objective was to maximize the number of apples packed without exceeding the box's capacity.
The optimal strategy is simple:
- Calculate the remaining capacity.
- Sort all apple weights in ascending order.
- Add apples from lightest to heaviest until no additional apple fits.
This classic greedy approach guarantees the maximum number of apples.
Question 5 — Student Score Stabilization
The final question was a simulation problem.
Students stand in a line, and every day each student's score changes according to the scores of their immediate neighbors:
- If both neighbors have higher scores, increase by one.
- If both neighbors have lower scores, decrease by one.
- The first and last students never change.
The process repeats until the entire array becomes stable.
The implementation is straightforward, but one important detail is that each day's updates must be calculated using a new array rather than modifying the original array in place. Otherwise, earlier updates would incorrectly affect later calculations within the same iteration.
Overall Difficulty
Overall, this OA focused much more on coding fundamentals than advanced algorithms.
The five questions mainly covered:
- String manipulation
- Greedy algorithms
- Simulation
- Basic mathematics
- Array processing
The difficulty level was generally Easy to Medium, making coding speed and careful implementation more important than knowing sophisticated algorithms.
If you're preparing for Virtu, practicing common HackerRank-style implementation problems will likely provide a significant advantage.
Preparation Tips
If you're getting ready for Virtu Trading or other quantitative trading firms such as Jane Street, Citadel, Optiver, IMC, or Hudson River Trading, I would recommend focusing on high-frequency HackerRank topics like strings, greedy algorithms, simulations, arrays, and mathematical implementation problems.
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