Decide whether a positive integer is an exact power of two (1, 2, 4, 8, 16, …).
Input
A single positive integer n.
Output
true if n is a power of two, otherwise false.
Power of Two
Easybit-manipulationmath
Examples
Example 1
- Input
1
- Output
true
1 is 2^0.
Example 2
- Input
16
- Output
true
16 is 2^4.
Example 3
- Input
18
- Output
false
18 = 10010 in binary — two bits set.
Constraints
- 1 <= n <= 10^18
Hints
Reveal hint 1
A power of two has exactly one bit set in binary.
Reveal hint 2
For a power of two, n AND (n-1) clears that one bit and leaves 0.
Reference solution (spoiler — try it yourself first)
Approach
A power of two has a single set bit, so n > 0 and (n & (n - 1)) == 0.
n = int(input())
print("true" if n > 0 and (n & (n - 1)) == 0 else "false")
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