Write largest_power_of_two(n) that returns the largest power of two (1, 2, 4, 8, 16, ...) that is less than or equal to n.
Examples
Input: n = 100
Output: 64
Input: n = 1
Output: 1
Constraints
1 <= n <= 10**18
Goals
- Grow a value by doubling inside a while loop
- Stop one step before overshooting a limit