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Sig·Software Engineer·Technical Phone Screen·Junior

Junior
Apr 2026

Summary

SIG quant engineer interview with a logic puzzle that sounds deceptively clean but turns out to need a full case analysis to crack. One question, no fluff.

Questions Asked (1)

Q1

A, B, and C each own some number of cats. The rule is: a person lies when speaking to someone with fewer cats than themselves, and tells the truth otherwise. Given four statements of the form 'X says to Y: [claim]', figure out exactly how many cats A owns by working through every possible ordering of cat counts and finding the one that's consistent.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

This wrecked me a little.

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AI HintsAI Generated

Suggested Approach

Model the problem as a constraint satisfaction puzzle: enumerate all possible assignments of cat counts to A, B, and C, then for each assignment, check whether each statement's truth value matches the speaker's lying/truth-telling rule. The consistent assignment(s) reveal A's cat count. Explain your reasoning step-by-step, emphasizing systematic enumeration and elimination.

Pro tip: Start by identifying the relative ordering of cat counts, since the lying rule depends only on who has more cats, not the exact numbers. This reduces the search space and makes the logic clearer.

1. Understand the rules and statements

Clarify that a person lies if and only if they speak to someone with fewer cats than themselves; otherwise they tell the truth. List the four statements with speakers and targets.

2. Enumerate possible orderings

List all 6 possible strict orderings of cat counts among A, B, and C (e.g., A>B>C, A>C>B, etc.). Consider that ties are possible only if the problem allows equal counts; if not, assume strict ordering.

3. Evaluate statements for each ordering

For each ordering, determine for each statement whether the speaker would lie or tell the truth based on the target's cat count relative to the speaker's. Then check if the statement's content matches that truth value.

4. Eliminate inconsistent orderings

Discard any ordering where at least one statement's truth value contradicts the lying rule. The remaining ordering(s) must be consistent with all statements.

5. Determine A's cat count

From the consistent ordering(s), deduce the exact number of cats A owns. If multiple orderings remain, use additional constraints (e.g., distinct counts) to narrow down to a unique answer.

Key Points to Mention

  • Constraint satisfaction and systematic enumeration
  • Logical implication and truth tables
  • Relative ordering vs. absolute counts
  • Elimination of inconsistent scenarios
  • Edge cases: ties, negative counts, zero cats
  • Verification of the final answer against all statements

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