Samsara·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Samsara SWE interview with a string parsing problem that looked manageable until you actually sat down with it. No regex allowed, which is the whole point of the pain.

Questions Asked (1)

Write a function that converts a custom link syntax like [text]("url") into proper HTML anchor tags, without using regular expressions. It needs to handle multiple links in a string, ignore malformed patterns, handle nested brackets by picking the innermost valid one, treat backslash-escaped characters as literals, and you should also analyze time/space complexity and write unit tests.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The no-regex constraint is what makes this actually hard.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline a stack-based single-pass parser that scans the string character by character, tracking bracket positions and escape states. After implementing, analyze time/space complexity and discuss trade-offs, then write unit tests covering normal, nested, escaped, and malformed inputs.

Pro tip: Mention that a stack naturally handles nested brackets and that you can record the start index of each '[' to extract the innermost valid link when a matching ']("url")' is found. Also note that escaping requires a state flag to treat the next character literally, which is a common pitfall.

1. Clarify requirements and edge cases

Ask questions to confirm the exact syntax, behavior for malformed patterns, nested brackets, and escaping rules. List edge cases like empty strings, multiple links, escaped brackets, and invalid URLs.

2. Design a stack-based parser

Use a stack to track indices of unmatched '[' characters. Iterate through the string, handling escapes and detecting the closing pattern ']("url")' to replace with an anchor tag.

3. Implement and handle edge cases

Write the function, ensuring malformed patterns are ignored, nested brackets resolve to the innermost valid link, and escaped characters are treated as literals. Build the output string incrementally.

4. Analyze complexity and trade-offs

State that time complexity is O(n) for a single pass and space complexity is O(n) for the stack and output. Discuss alternative approaches like recursive descent and why they might be less efficient.

5. Write unit tests

Create tests for basic conversion, multiple links, nested brackets, escaped characters, malformed patterns, and empty input. Use a testing framework like Jest or PyTest.

Key Points to Mention

Stack-based parsing to handle nested brackets and find innermost valid links.
Escape handling with a state flag to treat backslash-escaped characters as literals.
Single-pass O(n) time complexity and O(n) space complexity due to stack and output string.
Ignoring malformed patterns by only replacing when a complete valid pattern is found.
Unit tests covering edge cases: multiple links, nesting, escapes, malformed input, and empty string.
Trade-offs: no regex means more code but better control and performance; stack vs. recursion.

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