Power of Two with Bitwise

In Kotlin, there’s a neat bit trick to check if a number is a power of two:

fun isPowerOfTwo(n: Int): Boolean {
    return n > 0 && (n and (n - 1)) == 0
}

Why it works:
A power of two’s binary representation has exactly one bit set:

1   -> 0001
2   -> 0010
4   -> 0100
8   -> 1000

Subtracting 1 flips all bits after that 1 into 1s and clears the 1 bit itself:

8 (1000)  
7 (0111)

Now bitwise and doesn’t match with any bit, resulting in all 0:

1000
& 0111
------
0000

This makes the check extremely fast — no loops, no math functions — just pure bitwise magic 🙌🏼