Jerry.ai·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Interviewed for a software engineer role at Jerry.ai and got a string manipulation problem that looked deceptively simple at first glance. The follow-up asking for a linear time solution is where things got interesting.

Questions Asked (1)

Given two lowercase strings, determine whether the target string can be produced from the source string using at most one operation (insert a character, delete a character, replace one character with another, or move a character to a different position). Output a valid operation if one exists, 'no_change' if the strings are already equal, or 'impossible' if no single operation works.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I started by just enumerating the cases based on length difference, which got me pretty far.

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AI HintsAI Generated

Suggested Approach

First clarify the operation definitions and edge cases, then propose an efficient algorithm that handles all operations in a single pass or with minimal comparisons. Discuss time and space complexity, and consider trade-offs between simplicity and performance.

Pro tip: Mention that you would confirm whether 'move' is considered a single operation or if it's equivalent to a delete followed by an insert, as this affects the solution. Also, proactively discuss how to handle multiple valid operations by defining a priority order.

1. Clarify requirements and edge cases

Ask about the definition of 'move' (is it a single operation or two?), whether operations can be combined, and what to output if multiple operations are possible. Also consider empty strings, identical strings, and length differences.

2. Check for no change and length differences

If strings are equal, return 'no_change'. If length difference is more than 1, only a replace or move might work (but move doesn't change length), so check those cases separately.

3. Handle insert/delete/replace with two-pointer technique

For length difference of 1, use two pointers to find the first mismatch and verify the rest matches after skipping one character in the longer string (insert/delete). For equal lengths, check if exactly one character differs (replace).

4. Check for move operation

If no insert/delete/replace works, check if moving one character can transform source to target. This can be done by finding the first and last mismatch and verifying that removing one character from source and inserting it elsewhere yields target.

5. Return result and discuss complexity

Return the valid operation or 'impossible'. Analyze time complexity (O(n) for most checks) and space complexity (O(1) extra space). Mention potential optimizations or alternative approaches.

Key Points to Mention

Definition of 'move' operation and its implications
Two-pointer technique for insert/delete/replace detection
Handling multiple valid operations with a priority order
Time and space complexity analysis (O(n) time, O(1) space)
Edge cases: empty strings, identical strings, length differences >1
Trade-offs between different approaches (e.g., brute force vs. optimized)

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.