Capital One·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Apr 2026

Summary

Capital One SWE interview with a matrix manipulation problem. Nothing too wild conceptually but the rotate command tripped me up more than I expected.

Questions Asked (1)

Given an integer matrix and a list of string commands, implement each command (reverseRow, swap rows, or 90-degree clockwise rotation) and return the final matrix state.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The reverseRow and swap parts were fine, pretty mechanical.

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AI HintsAI Generated

Suggested Approach

Clarify the matrix dimensions, command semantics, and edge cases before coding. Choose an in-place or copy-based implementation based on constraints, then implement each command as a separate function and test with small examples. Discuss time/space complexity and potential optimizations.

Pro tip: Mention that rotation can be done in-place by first transposing the matrix and then reversing each row, which saves memory and shows deeper understanding. Also, proactively ask about command frequency and matrix size to decide between eager and lazy execution.

1. Clarify requirements and edge cases

Ask about matrix dimensions, command formats, and whether commands can be invalid. Confirm if the matrix should be modified in-place or if a new matrix is acceptable.

2. Design command implementations

For each command, outline the algorithm: reverseRow reverses a specific row; swapRows swaps two rows; rotate90Clockwise can be done by transposing and reversing rows. Consider using helper functions for clarity.

3. Analyze complexity and trade-offs

Discuss time and space complexity for each command and the overall sequence. Compare in-place vs. copy approaches, and mention potential optimizations like lazy rotation if many commands are given.

4. Implement and test

Write clean code with meaningful variable names, handle edge cases (e.g., empty matrix, single row/column), and walk through a small example to verify correctness.

5. Review and optimize

Check for off-by-one errors, ensure rotation is correct, and consider if any commands can be combined or if the matrix representation can be changed for efficiency.

Key Points to Mention

Matrix representation and indexing (0-based vs 1-based)
In-place vs. out-of-place operations and memory implications
Time complexity: O(m*n) for rotation, O(n) for row operations
Space complexity: O(1) extra for in-place, O(m*n) for copy
Edge cases: empty matrix, single row/column, invalid commands
Testing strategy: unit tests for each command and integration test for sequence

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