Check whether an integer is a power of two
Company: Snapchat
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: hard
Interview Round: Onsite
Given a signed 32-bit integer `n`, return `true` if `n` is an exact power of 2, otherwise return `false`.
A power of 2 is a number of the form `2^k` where `k >= 0` (e.g., 1, 2, 4, 8, 16, ...).
## Input
- `n`: an integer in the range `[-2^31, 2^31 - 1]`
## Output
- Boolean indicating whether `n` is a power of 2.
## Examples
- `n = 1` → `true` (2^0)
- `n = 16` → `true` (2^4)
- `n = 3` → `false`
- `n = 0` → `false`
- `n = -8` → `false`
## Follow-up
- Aim for an `O(1)` / bit-manipulation solution (no loops over bits, and no precomputed set/table of powers).
Quick Answer: This question evaluates proficiency in bit-level reasoning and integer arithmetic, specifically understanding binary representations and the properties that define powers of two.
Return whether n is a positive power of two using bit manipulation.
Constraints
- Inputs are Python literals matching the function signature.
- Return a deterministic exact-match value.
Examples
Input: (1,)
Expected Output: True
Explanation: 1 is 2^0.
Input: (16,)
Expected Output: True
Explanation: 16 is a power of two.
Input: (3,)
Expected Output: False
Explanation: 3 has multiple set bits.
Input: (0,)
Expected Output: False
Explanation: Zero is not positive.
Input: (-8,)
Expected Output: False
Explanation: Negative numbers are not powers of two.
Hints
- Clarify edge cases before coding.
- Keep the return value deterministic.