Hello everyone! I recently completed a ByteDance Online Assessment hosted on CodeSignal, which follows a very similar format to TikTok's coding assessments. The test consisted of 4 programming questions with a total time limit of 70 minutes.
Fortunately, the questions I received were all from commonly seen CodeSignal-style patterns. From reading the problems to submitting all solutions, I spent less than twenty minutes and used the remaining time to review edge cases and optimize my code. In the end, I successfully passed the assessment.
ByteDance OAs primarily focus on practical programming skills. While the time limit can feel tight, candidates who have practiced similar CodeSignal questions beforehand will likely find the test manageable. Below is a detailed breakdown of the four questions and the approaches I used.
Question 1: User Rating Tier Calculation
The first problem involved determining a user's final ranking tier based on an initial rating and a list of rating changes.
After applying all rating adjustments, the final score must be mapped to one of four tiers:
- beginner
- intermediate
- advanced
- pro
The solution was straightforward. I summed the initial rating and all values in the changes array, then used simple conditional checks to determine the corresponding tier.
The main consideration was handling boundary values correctly, especially ratings that landed exactly on threshold values such as 1000, 1500, and 2000.
Question 2: Reverse the Middle of Vowel-Bounded Words
This problem focused on string manipulation.
Given an array of words, if both the first and last character of a word are vowels (case-insensitive), the middle portion of the word should be reversed while keeping the first and last characters unchanged.
Examples:
- apple → alppe
- OranGe → OGnare
- banana → unchanged
I created a vowel lookup set containing both uppercase and lowercase vowels. For each word, I checked whether its first and last characters belonged to the set.
If the condition was satisfied and the length exceeded two characters, I reversed the middle substring and reconstructed the word. Otherwise, I kept the original word unchanged.
The problem was relatively simple but required careful handling of short strings with lengths of one or two characters.
Question 3: Circular Battery Usage Simulation
This was the most simulation-heavy problem of the assessment.
A device needs to remain powered for t minutes. Several batteries are available, and each battery has:
- A capacity (how many minutes it can power the device)
- A recharge time
After a battery is used, it enters a charging state and becomes unavailable until fully recharged. The batteries are checked in a circular order. If a battery is still charging, it is skipped.
The objective is to determine the minimum number of fully charged batteries required to keep the device running for the entire duration. If a situation occurs where all batteries are simultaneously unavailable, the answer should be -1.
I solved this using direct simulation.
An array stored the next available timestamp for each battery. At every step, I searched for a battery that could be used at the current time. Once selected, I updated the current time, increased the usage count, and calculated when the battery would become available again.
If no battery could be used at a given moment, the simulation immediately returned -1.
The implementation was not particularly difficult, but careful attention was needed when managing battery rotation and availability updates.
Question 4: Reconstructing a Travel Route from Adjacent Photos
The final problem involved rebuilding a travel itinerary.
A traveler visited multiple landmarks, but only a collection of photos remained. Each photo recorded two consecutively visited landmarks, although the travel direction was unknown.
The problem guaranteed that all landmarks formed a single path without branches.
The solution was essentially graph reconstruction.
I built an undirected adjacency list and calculated the degree of each node. Since the graph represented a path, one of the endpoints would have degree 1.
Starting from an endpoint, I repeatedly moved to the neighboring node that was not previously visited. By continuing this process until all nodes were traversed, I reconstructed the complete travel route.
Because the graph was guaranteed to be a simple chain, no complex DFS or BFS was required.
Overall Difficulty and Preparation Tips
Overall, the ByteDance OA felt easier than many candidates expect. The problems primarily tested:
- Basic programming fundamentals
- String manipulation
- Simulation techniques
- Simple graph construction and traversal
If you regularly practice CodeSignal-style questions, most of these patterns will become familiar very quickly.
My recommendations for future candidates are:
- Practice string-processing problems extensively.
- Become comfortable with simulation-based questions.
- Review graph fundamentals, especially path reconstruction problems.
- Pay close attention to edge cases and boundary conditions.
- Build familiarity with common CodeSignal question patterns.
In my experience, prior exposure to similar problems dramatically improves both speed and accuracy during the assessment.
Additional Preparation Resources
One thing I noticed while preparing is that simulation and optimization problems can become time-consuming if encountered for the first time during an actual assessment.
For candidates looking to maximize their chances of success, structured preparation and targeted guidance can make a significant difference.
You can explore additional interview preparation resources, OA guidance, and technical interview support at Interview Aid.
Whether you're preparing for ByteDance, TikTok, or other CodeSignal-based assessments, feel free to share your experiences and discuss strategies with fellow candidates.
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