Sig·Software Engineer·Technical Phone Screen·Junior

Junior

May 2026

Summary

SIG quant researcher interview with a combinatorics seating puzzle. Pretty niche problem that felt more like a math olympiad warmup than anything I'd seen in prep materials.

Questions Asked (1)

Five toddlers (Anna, Brian, Charlie, Dixie, Eva) need to be seated at a round table with the following constraints: Anna won't sit next to Brian or Eva, Brian won't sit next to Charlie, and Dixie won't sit next to Eva or Charlie. Given that Dixie sits immediately to the left of Anna, and Anna sits immediately to the left of Brian, who sits immediately to the left of Brian?

Algorithms & Data Structures

Author's notes

I stared at this for an embarrassingly long time.

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AI HintsAI Generated

Suggested Approach

First, recognize that the question contains a logical contradiction: if Anna sits immediately to the left of Brian, then Brian cannot sit immediately to the left of himself. Therefore, the question 'who sits immediately to the left of Brian?' is invalid. Instead of solving the seating arrangement, point out the inconsistency and explain why no valid answer exists.

Pro tip: In interviews, when a question seems impossible or contradictory, don't force an answer—demonstrate critical thinking by identifying the flaw and explaining it clearly. This shows you prioritize correctness over guessing.

1. Parse the given conditions

List all constraints, especially the fixed positions: Dixie is immediately left of Anna, and Anna is immediately left of Brian.

2. Check for logical consistency

Determine if the conditions can all be true simultaneously. Notice that 'Anna sits immediately to the left of Brian' directly answers the question, but the question asks who sits left of Brian, which would be Anna—yet the phrasing implies a different person.

3. Identify the contradiction

Realize that if Anna is left of Brian, then Brian cannot be left of himself. The question 'who sits immediately to the left of Brian?' is therefore nonsensical because it assumes Brian is both to the left and right of Anna.

4. Formulate a clear response

State that the question is invalid due to contradictory constraints, and explain that no valid seating arrangement exists that satisfies all conditions.

Key Points to Mention

The condition 'Anna sits immediately to the left of Brian' directly answers the question, but the question asks for someone else, creating a paradox.
The constraints are mutually inconsistent because they imply Brian is to the left of himself.
In a round table, 'left of' is relative to the person's perspective, but the given conditions still lead to a contradiction.
The correct approach is to identify the logical flaw rather than attempt to solve an impossible puzzle.
This demonstrates attention to detail and logical reasoning, which are crucial for software engineering.
If the question intended to ask 'who sits immediately to the right of Brian?', the answer would be Anna, but as stated, it's invalid.

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