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Airbnb·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Airbnb SWE interview with a URL parsing problem that looks straightforward until you actually read the constraints. The mixed value types and non-unique keys are where it gets interesting.

Questions Asked (1)

Q1

Given a GET request URL, parse the query string and return each key-value pair as a Map. Keys may repeat, and values can be integers, strings, booleans, or lists.

Algorithms & Data StructuresAPI & Integrations
Author's notes

I started coding before fully thinking through the value type logic and had to backtrack twice.

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AI HintsAI Generated

Suggested Approach

Clarify the expected behavior for repeated keys and type inference, then design a parser that splits the query string, URL-decodes each component, and infers types. Use a Map<String, Object> where repeated keys are collected into a List, and handle edge cases like missing values and encoded characters.

Pro tip: Discuss how you would handle ambiguous type inference (e.g., '123' as integer vs string) and propose a configurable or heuristic-based approach, showing awareness of real-world API design trade-offs.

1. Clarify Requirements and Edge Cases

Ask about expected behavior for repeated keys, type inference rules, URL encoding, and handling of keys without values. Confirm the output format and any constraints.

2. Parse the Query String

Extract the query string from the URL, split by '&' to get key-value pairs, and split each pair by '=' to separate keys and values. Handle cases where '=' is missing.

3. Decode and Infer Types

URL-decode keys and values. For each value, attempt to infer its type: check for boolean ('true'/'false'), integer (numeric), or string. If a key repeats, collect values into a list.

4. Build the Map

Construct a Map<String, Object> where each key maps to a single value or a List of values if repeated. Ensure type consistency and handle potential conflicts.

5. Test and Validate

Walk through examples including edge cases: repeated keys, encoded characters, empty values, and mixed types. Verify the output matches expectations.

Key Points to Mention

  • Handling repeated keys by aggregating values into a List
  • Type inference strategy: boolean, integer, string, and list detection
  • URL decoding using appropriate libraries or built-in functions
  • Edge cases: missing '=', empty values, encoded characters, and keys without values
  • Choice of data structure: Map<String, Object> to accommodate different value types
  • Time and space complexity analysis of the parsing algorithm

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