I just finished HRT's Online Assessment on July 27. The OA was hosted on CodeSignal and consisted of four coding problems to be completed in 70 minutes.
The biggest takeaway is that the question pattern is extremely consistent. The first two problems are relatively straightforward, the third focuses on matrix simulation, and the fourth requires an optimized data structure solution. If you've practiced CodeSignal OAs for companies like TikTok, Uber, Visa, or Capital One, this set will feel very familiar because they all draw from essentially the same CodeSignal question pool.
Here's a breakdown of all four problems for anyone preparing for upcoming CodeSignal assessments.
Problem 1: Highest Value Product
You're given two arrays: prices and ratings (ratings range from 1 to 5). Return the index of the product with the highest rating / price ratio. If multiple products have the same ratio, return the smallest index.
The solution is simply a single pass through the arrays while maintaining the current best ratio and its index. When two ratios are equal, keep the smaller index. To avoid floating-point precision issues, you can compare fractions using cross multiplication instead of division.
This is a classic warm-up problem that usually takes only a few minutes.
Problem 2: Bird Nest Building
The array represents branches scattered along a path. Positive integers indicate branch lengths, while 0 represents empty positions. A bird starts from one of the zero positions, repeatedly searches for the nearest branch on the right, then the nearest on the left, alternating directions until the total collected branch length reaches at least 100.
This is a straightforward simulation problem. Maintain the current search direction, locate the nearest available branch in that direction, add its length, set its position to zero, and switch directions.
The most common bug is failing to handle the situation where one side has no remaining branches. Make sure your simulation terminates correctly instead of entering an infinite loop.
Problem 3: Longest Diagonal Pattern
The matrix contains only the values 0, 1, and 2. Find the longest diagonal segment that starts with 1 and then follows the repeating pattern:
1, 2, 0, 2, 0, 2, 0, ...The sequence must end exactly on the boundary of the matrix. All four diagonal directions need to be considered.
The typical solution is to enumerate every cell containing 1 as a starting point, then explore each diagonal direction while verifying that every element matches the required pattern.
Only update the answer if the entire sequence remains valid and the final position lies on the matrix boundary. Stop immediately when the pattern breaks.
The trickiest part is mapping each position in the traversal to the expected value in the repeating sequence, so it's worth writing that logic carefully before coding.
Problem 4: Unique Bytes Covered
Each operation provides an interval [start, end] representing received bytes. Intervals may overlap. After every insertion, output the total number of unique bytes covered so far.
This is the classic interval union problem.
Maintain an ordered collection of merged intervals. Whenever a new interval arrives, merge all overlapping ranges and update the total covered length accordingly.
Since the coordinate range can be very large, allocating an array is not feasible. An ordered map, balanced tree, or other dynamic interval structure is the intended solution.
Overall Thoughts
Once you're comfortable with the standard CodeSignal 70-minute format, the first two problems become warm-ups. Most of your time should be reserved for the third and fourth questions.
If you're preparing for companies that use CodeSignal, matrix traversal, simulation problems, and interval merging are three topics that deserve the most practice. These patterns appear repeatedly across assessments from HRT, TikTok, Uber, Visa, Capital One, and many other companies.
Preparing for CodeSignal Interviews?
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Good luck with your OA, and hope to see you on the other side of the interview process!
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