Kickoff·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jul 2026

Summary

Kickoff had me implement a full truth table generator from a string boolean expression, which sounds manageable until you realize they want parsing, precedence handling, variable extraction, and complexity analysis all in one shot. Pretty dense technical screen for a software engineer role.

Questions Asked (2)

Implement a function that takes a string boolean expression and outputs a complete truth table. Variables are single uppercase letters, operators include '!' for NOT, adjacency for implicit AND, and '+' for OR, with parentheses allowed and spaces ignored. You need to parse the expression, extract and sort all distinct variables, enumerate all 2^n assignments, and print the truth table rows.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The implicit AND part is what tripped me up first.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the grammar and edge cases, then outline a recursive descent parser that builds an AST. After parsing, collect variables, evaluate the expression for all assignments, and print the truth table in a clear format.

Pro tip: Mention that you would use a recursive descent parser because it naturally handles operator precedence and parentheses, and it's easy to extend. Also, discuss how to handle edge cases like empty expressions or invalid syntax gracefully.

1. Clarify requirements and edge cases

Ask about operator precedence, associativity, and how to handle invalid input. Confirm the output format and whether variables should be sorted alphabetically.

2. Design the parser

Outline a recursive descent parser with functions for expression, term, and factor to handle OR, implicit AND, NOT, and parentheses. Consider using a tokenizer to ignore spaces.

3. Build and evaluate the AST

Construct an abstract syntax tree (AST) from the parsed tokens. Then, recursively evaluate the AST for each variable assignment.

4. Enumerate assignments and generate table

Extract distinct variables, sort them, and iterate over all 2^n combinations. For each, evaluate the expression and format the row with variable values and the result.

5. Test and optimize

Test with various expressions, including edge cases. Discuss potential optimizations like memoization or iterative evaluation for large n.

Key Points to Mention

Operator precedence: NOT > AND > OR, and how implicit AND is handled.
Recursive descent parsing technique and its advantages.
Handling parentheses and ignoring spaces.
Extracting and sorting distinct variables.
Enumerating all 2^n assignments efficiently.
Output formatting and potential edge cases (e.g., empty expression, single variable).

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

Describe your parsing approach for this expression language and discuss edge cases like unmatched parentheses, unknown symbols, or empty input.

Algorithms & Data StructuresSystem Design

Author's notes

They pushed pretty hard on edge cases after I had the main solution.

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AI HintsAI Generated

Suggested Approach

Start by outlining a standard parsing strategy such as recursive descent or a stack-based approach, then explicitly discuss how you handle edge cases like unmatched parentheses, unknown symbols, and empty input. Emphasize error detection and recovery, and tie your approach to the specific expression language's grammar.

Pro tip: Demonstrate maturity by discussing not just error detection but also error recovery and user-friendly error messages, and mention how you would test edge cases with unit tests.

1. Define the Grammar

Briefly describe the expression language's grammar (e.g., arithmetic expressions with parentheses) to set context for parsing decisions.

2. Choose a Parsing Strategy

Explain your chosen approach (e.g., recursive descent, shunting-yard, or stack-based) and justify why it suits the grammar and requirements.

3. Handle Edge Cases

Detail how you detect and handle unmatched parentheses, unknown symbols, and empty input, including error reporting and recovery.

4. Discuss Error Recovery

Explain how you might recover from errors to continue parsing or provide meaningful feedback, rather than just failing.

5. Testing and Validation

Mention how you would test the parser, including unit tests for edge cases and possibly fuzz testing.

Key Points to Mention

Recursive descent parsing with explicit error handling for unmatched parentheses.
Stack-based approach for tracking parentheses and detecting mismatches.
Tokenization and handling unknown symbols by reporting lexical errors.
Empty input handling: return a default value or error depending on language semantics.
Error recovery techniques like panic mode or synchronization to continue parsing.
Unit testing and fuzz testing to ensure robustness against edge cases.

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