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Snapchat·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Snapchat coding screen, one algorithmic problem the whole time. The question was cleaner than I expected but I still fumbled the explanation of why the approach works.

Questions Asked (1)

Q1

Given an array of distinct prime numbers, return all distinct products formed by multiplying any non-empty subset of them, sorted in ascending order.

Algorithms & Data Structures
Author's notes

My first instinct was to just brute-force enumerate subsets and collect products into a set, but the interviewer pushed me on why I didn't need the set at all.

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AI HintsAI Generated

Suggested Approach

Clarify that the input consists of distinct primes, so all subset products are unique. Use a recursive backtracking or iterative generation approach to build all non-empty subset products, then sort the results. Discuss time and space complexity, noting that the number of products is 2^n - 1, so the solution is exponential in the worst case.

Pro tip: Mention that since the primes are distinct, there is no need to deduplicate products; this simplifies the implementation and avoids unnecessary overhead. Also, consider using a BFS-style generation to produce products in ascending order without a final sort, which could be more efficient if the primes are sorted.

1. Clarify constraints and edge cases

Confirm that the array contains distinct primes, the array size, and whether the output should include 1 (it should not, as subsets must be non-empty). Discuss handling of empty input.

2. Choose generation strategy

Decide between recursive backtracking, iterative bitmask, or BFS generation. Explain that since all products are distinct, any method works, but BFS can yield sorted order if primes are sorted.

3. Implement product generation

Write code to generate all subset products. For example, start with an empty list, and for each prime, add new products by multiplying the prime with existing products and the prime itself.

4. Sort and return results

If not already sorted, sort the list of products in ascending order. Return the sorted list.

5. Analyze complexity and optimize

State that time complexity is O(2^n) for generation and O(2^n log 2^n) for sorting, which is optimal since output size is exponential. Space complexity is O(2^n) for storing results.

Key Points to Mention

  • Distinct primes guarantee unique products, so no deduplication is needed.
  • The number of non-empty subsets is 2^n - 1, leading to exponential time and space complexity.
  • Recursive backtracking or iterative bitmask are straightforward approaches.
  • Sorting is required unless using a BFS approach that maintains sorted order.
  • Edge cases: empty array, single element, and large n (discuss feasibility).
  • Potential optimization: use a min-heap to generate products in sorted order without full sort, but trade-offs exist.

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