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Snap·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Snap SWE screen with a pretty basic coding problem. Nothing fancy, just a bit-manipulation type question that you either know or you don't.

Questions Asked (1)

Q1

Given a list of integers, write a function that returns 1 for each integer that is a power of 2, and 0 otherwise.

Algorithms & Data Structures
Author's notes

Classic bit trick question.

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AI HintsAI Generated

Suggested Approach

Clarify the problem constraints (e.g., input size, integer range, handling of non-positive numbers) and then present an efficient bitwise solution using n > 0 && (n & (n - 1)) == 0. Walk through the logic, discuss time and space complexity, and mention edge cases like 0, 1, and negative numbers.

Pro tip: Mention that the bitwise trick works because powers of two have exactly one set bit, and subtracting 1 flips all bits below it, so the AND is zero. Also note that in languages like Java, you should use n > 0 to exclude negative numbers because of two's complement representation.

1. Clarify requirements and constraints

Ask about input size, integer range, whether the list can be empty, and how to handle 0 and negative numbers. Confirm the expected output format (e.g., list of 1s and 0s).

2. Explain the bitwise property

State that a positive integer is a power of two if and only if it has exactly one bit set. Show that n & (n - 1) clears the lowest set bit, so the result is 0 for powers of two.

3. Write the function

Implement the function that iterates through the list and applies the condition n > 0 && (n & (n - 1)) == 0, returning 1 or 0 accordingly. Use clear variable names and handle edge cases.

4. Analyze complexity and test

State that time complexity is O(n) and space complexity is O(1) per element (or O(n) for the output). Walk through test cases: [1, 2, 3, 4, 0, -2] should yield [1,1,0,1,0,0].

5. Discuss alternatives and trade-offs

Mention that a loop dividing by 2 repeatedly is O(log n) per number but less efficient; the bitwise method is optimal. Also note that for very large lists, parallelization or vectorization could be considered.

Key Points to Mention

  • Bitwise AND trick: n & (n - 1) == 0 for powers of two
  • Need to check n > 0 to exclude zero and negative numbers
  • Time complexity O(n) for n integers, space O(1) extra
  • Edge cases: 0, 1, negative numbers, and empty list
  • Alternative approaches: repeated division by 2 or using logarithms
  • Language-specific considerations (e.g., integer overflow, two's complement)

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