Check if a Number Is a Power of Two (Bit Level)

Question

## Problem

Determine whether an integer is a power of two using bit manipulation, no loops or division.

## Example
```
8 -> true, 6 -> false
```

## Constraints
- -2^31 ≤ n ≤ 2^31-1

## Approach
`n > 0 && (n & (n-1)) == 0`. Intel loves bit-level reasoning — explain why it works.