Capital One·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Capital One software engineer interview with a matrix manipulation coding problem. Pretty straightforward algorithmic question but there are a few edge cases that can trip you up if you're not careful.

Questions Asked (1)

Given an n x m integer matrix and a list of commands, implement a function that processes each command sequentially and returns the resulting matrix. The commands are: reverse the elements in a specified row, swap two specified rows, and rotate the entire matrix 90 degrees clockwise.

Algorithms & Data Structures

Author's notes

The row operations were fine, reversing and swapping are pretty mechanical.

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AI HintsAI Generated

Suggested Approach

Clarify the command format and edge cases, then design a solution that processes commands sequentially, mutating the matrix in place when possible. For each command, implement the operation efficiently, paying attention to row/column indices and matrix dimensions after rotation.

Pro tip: Discuss the trade-offs between in-place operations and creating new matrices, and mention how you would test with edge cases like 1x1 matrices or empty commands.

1. Clarify requirements and constraints

Ask about the command format, matrix dimensions, and whether the matrix should be modified in place or a new matrix returned. Confirm edge cases like empty commands or invalid indices.

2. Design data structures and operations

Decide on representation (e.g., list of lists) and implement helper functions for each command: reverse row, swap rows, and rotate 90 degrees clockwise.

3. Process commands sequentially

Iterate through the command list, applying each operation to the current matrix state. Ensure that after rotation, subsequent commands refer to the new dimensions.

4. Handle edge cases and validate

Check for invalid row indices, empty matrices, and commands that might not apply (e.g., swapping rows when only one row exists). Test with small examples.

5. Analyze complexity and optimize

Discuss time and space complexity of each operation and overall. Consider optimizations like lazy rotation or using transpose and reverse for rotation.

Key Points to Mention

Command parsing and representation (e.g., tuples or strings)
In-place vs. new matrix trade-offs
Efficient rotation: transpose then reverse each row
Handling index bounds and matrix dimensions after rotation
Time complexity: O(n*m) per rotation, O(m) per row reversal, O(1) for swap if using references
Testing strategy: unit tests for each command and integration tests

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