Minimum window substringCodingGiven strings s and t, return the shortest substring of s that contains every character of t, counting repeats, or an empty string if there is none. Grow the window until it…
Last asked May 2026
Character.AI technical phone screen interview
Round 3 of 8 · 3 questions reported
- Length
- 60 min
- Format
- Live coding, usually in Python
- They grade
- Talking through the approach and edge cases counts as much as a working solution
- Heads-up
- A data structures problem at medium level (one guide says about two in 45 minutes), then a short talk on distributed systems or model inference.
Questions Character.AI asks in this round 3
- How strings are stored and what copying them costsCodingWhat is a string under the hood? Describe the fields a string struct holds and how you would implement one yourself, then give the time cost of copying a string and of common…Possibly retired
- Temporal key-value store with point-in-time reads and restoreCodingBuild an in-memory key-value store that keeps every version of every key, so you can ask what a key held at any point in time. Implement the TemporalKVStore class: -…Possibly retired