clickup·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Apr 2026

Summary

Interviewed for a Software Engineer role at ClickUp and got a coding problem about simulating a document editor with line-based insert and delete operations. Pretty niche problem, not your typical LeetCode array question.

Questions Asked (1)

You're given a document as a list of strings (one per line, 1-indexed) and a sequence of events. Each event is either an Insert (adding one or more lines at a given position, shifting existing lines down) or a Delete (removing a count of consecutive lines starting at a given position). Handle edge cases like inserting at line 0, inserting past the end, deleting past the end, deleting from an empty document, and empty content lists. Return the final document after processing all events.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The line-number semantics tripped me up more than I expected.

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AI HintsAI Generated

Suggested Approach

Clarify the event format and edge-case semantics first, then propose a straightforward list-based simulation with careful index normalization and bounds checking. Walk through a small example to validate the logic, and discuss complexity and potential optimizations like a balanced tree or rope for large inputs.

Pro tip: Explicitly state your assumptions about 1-indexing and edge-case behavior (e.g., inserting at line 0 means prepend, inserting past end appends, deleting past end removes available lines) before coding, and ask the interviewer to confirm—this shows attention to detail and prevents wasted effort.

1. Clarify requirements and edge cases

Ask about the exact event format, whether positions are 1-indexed, and the expected behavior for edge cases like inserting at 0, inserting past the end, deleting past the end, and empty documents. Confirm whether empty content lists are allowed and how they should be handled.

2. Choose data structure and outline algorithm

Decide on a simple list (array) for clarity, or a more efficient structure like a balanced BST or rope if performance matters. Outline the algorithm: iterate through events, convert 1-indexed positions to 0-indexed, clamp positions to valid range, and perform insert or delete operations.

3. Walk through a concrete example

Trace a small example with several events, including edge cases, to verify the logic and demonstrate correctness. Show how the document changes after each event.

4. Analyze complexity and trade-offs

Discuss time and space complexity of the chosen approach. For a list, insertion/deletion is O(n) per event, leading to O(m*n) total. Mention alternatives like a balanced tree or rope that can achieve O(log n) per operation, and when they might be preferable.

5. Handle edge cases explicitly

Enumerate all edge cases and describe how your code handles them: inserting at line 0 (prepend), inserting past the end (append), deleting past the end (delete to end), deleting from an empty document (no-op), and empty content lists (no-op).

Key Points to Mention

1-indexing vs 0-indexing and how to convert positions correctly
Clamping positions to valid range to handle out-of-bounds inserts and deletes
Time complexity of list-based simulation and potential optimizations (e.g., balanced tree, rope)
Edge case: inserting at line 0 means prepend, not error
Edge case: deleting past the end should remove only available lines, not throw an error
Handling empty content lists and empty documents gracefully

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