C# Power of 2 Program

What Is a Power of 2?

A positive integer is a power of 2 when it equals 2k for some integer k ≥ 0. In binary, that means exactly one bit is set.

Powers of 2: 1, 2, 4, 8, 16, 32, 64, ...

Binary (one bit set):
   1 → 1
   2 → 10
   4 → 100
   8 → 1000
  16 → 10000

Not: 0, 3, 6, 12, 18, negatives

How to Check a Power of 2 in C#

Four clear steps — then pick the bitwise trick or a divide-by-2 loop.

1. Require n > 0.
2. Prefer the interview classic: (n & (n - 1)) == 0.
3. Or keep dividing by 2 while n is even; end at 1 if it is a power of two.
4. Reject zero and negatives before either test.

Pseudocode

function IsPowerOfTwo(n):
    return n > 0 and (n & (n - 1)) == 0

// Loop alternative:
function IsPowerOfTwoLoop(n):
    if n <= 0: return false
    while n % 2 == 0:
        n = n / 2
    return n == 1

Cheat Sheet

Keep these facts handy while writing the program.

Live Preview

Enter an integer to see the bitwise check and the power-of-two verdict.

n = 8
n - 1 = 7
n & (n - 1) = 0
8 is a power of 2

Worked Walkthrough — n = 8

Show the bitwise identity, then the same answer by dividing.

Bitwise:
  8 in binary = 1000
  7 in binary = 0111
  1000 & 0111 = 0000  → power of 2

Divide-by-2 loop:
  8 / 2 = 4
  4 / 2 = 2
  2 / 2 = 1
  stop at 1 → power of 2

Counterexample n = 6:
  6 = 110, 5 = 101
  110 & 101 = 100 ≠ 0 → not a power of 2

C# Programs

Start with the bitwise one-liner — that is the usual interview answer. Keep the divide loop ready when you need to explain without bits.

using System;

class Program
{
    static bool IsPowerOfTwo(int n)
    {
        return n > 0 && (n & (n - 1)) == 0;
    }

    static void Main()
    {
        int number = 8;
        Console.WriteLine(number + (IsPowerOfTwo(number) ? " is a power of 2" : " is not a power of 2"));
    }
}

8 is a power of 2

using System;

class Program
{
    static bool IsPowerOfTwo(int n)
    {
        if (n <= 0)
        {
            return false;
        }

        while (n % 2 == 0)
        {
            n /= 2;
        }

        return n == 1;
    }

    static void Main()
    {
        Console.WriteLine(IsPowerOfTwo(1));  // True
        Console.WriteLine(IsPowerOfTwo(8));  // True
        Console.WriteLine(IsPowerOfTwo(6));  // False
        Console.WriteLine(IsPowerOfTwo(0));  // False
    }
}

True
True
False
False

Time and Space Complexity

Prefer bitwise in code and interviews. Use the loop when explaining the idea without bit operations.

Key Takeaways