Bloomberg·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Jun 2026

Summary

Bloomberg SWE interview where they had me implement a stripped-down version of grep from scratch. The focus wasn't on clever algorithms but on how cleanly you structure the code and whether adding a new flag later would be painful or trivial.

Questions Asked (1)

Implement a simplified grep utility that takes a pattern, a list of lines, and optional flags (case-insensitive, line numbers, invert match) and returns the matching lines in order.

System DesignTechnical Trade-offsAlgorithms & Data Structures

Author's notes

The problem itself isn't hard but I spent too long on the actual matching logic and not enough on the flag abstraction layer, which is clearly what they cared about.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline a clean function signature that separates pattern matching from flag handling. Implement the core matching logic with a simple loop, applying flags as filters, and discuss trade-offs like regex vs literal matching and performance considerations.

Pro tip: Mention that you would compile the pattern once if using regex, and precompute the case-insensitive version to avoid repeated conversions. Also, discuss how to handle large inputs efficiently, e.g., streaming lines instead of loading all into memory.

1. Clarify requirements and edge cases

Ask about pattern type (literal vs regex), flag interactions (e.g., invert with case-insensitive), empty pattern, empty lines, and expected output format (with line numbers).

2. Design the function signature and data flow

Define a function that takes pattern, lines, and flags, and returns a list of matching lines (or tuples with line numbers). Outline how flags will be applied in sequence.

3. Implement core matching logic

Iterate through lines, apply case-insensitive transformation if needed, check for pattern match, apply invert if set, and collect results with line numbers if requested.

4. Optimize and discuss trade-offs

Consider precompiling regex, using efficient string operations, and handling large inputs via streaming. Discuss time/space complexity and potential improvements.

5. Test with examples and edge cases

Walk through a few test cases covering all flags, empty inputs, and special characters to validate correctness and robustness.

Key Points to Mention

Flag handling order and interactions (e.g., case-insensitive before invert)
Regex vs literal matching and performance implications
Line numbering: 1-based indexing and output format
Memory efficiency: streaming vs loading all lines
Edge cases: empty pattern, empty lines, special characters
Time and space complexity analysis

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