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SIG (Susquehanna)·Data Scientist·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
May 2026

Summary

Interviewed for a Data Scientist role at SIG and got hit with a classic knights and knaves logic puzzle. Pretty representative of the kind of lateral thinking they seem to value there.

Questions Asked (1)

Q1

On an island of knights (always truthful) and knaves (always lying), person B says to person A: 'You always lie.' Which role assignments are logically consistent, and why?

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

I stared at this for a second because it looks simple but you have to be careful about each case.

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AI HintsAI Generated

Suggested Approach

Enumerate all four possible role assignments for A and B, then check each against the statement 'You always lie' and the truthfulness constraints of knights and knaves. Identify which assignments lead to a contradiction and which are consistent, explaining the logical reasoning for each.

Pro tip: After solving, briefly relate the puzzle to data science concepts like constraint satisfaction or boolean logic, showing how you connect abstract reasoning to practical problem-solving.

1. Understand the rules

Knights always tell the truth; knaves always lie. The statement 'You always lie' is about person A's truthfulness.

2. Enumerate possible assignments

List all four combinations: A=Knight, B=Knight; A=Knight, B=Knave; A=Knave, B=Knight; A=Knave, B=Knave.

3. Evaluate each assignment

For each, determine if B's statement is true or false, and check if it matches B's role (truth-teller or liar). Also ensure A's role is consistent with the statement's content.

4. Identify consistent assignments

Find which assignments have no contradictions. Explain why the others fail.

5. Summarize and conclude

State the final consistent role assignments and the logical reasoning behind them.

Key Points to Mention

  • Definition of knights and knaves: knights always tell the truth, knaves always lie.
  • The statement 'You always lie' is equivalent to 'A is a knave'.
  • Case analysis: If B is a knight, the statement must be true, so A is a knave. This is consistent.
  • If B is a knave, the statement must be false, so A is not a knave, meaning A is a knight. This is also consistent.
  • Therefore, two assignments are consistent: (A=Knave, B=Knight) and (A=Knight, B=Knave).
  • The other assignments lead to contradictions: if both are knights, B's true statement would falsely call A a knave; if both are knaves, B's false statement would incorrectly call A a knave (since A would be a knave, making the statement true, which a knave cannot say).

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