How to find the position of the first set bit (1-bit) of a number in Kotlin

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import kotlin.math.log2

// Function to find the position of the first set bit
fun findFirstSetBitPosition(num: Int): Int {
    // Edge case: If the number is 0, there are no set bits
    if (num == 0) {
        return 0 // Return 0 to indicate no set bit
    }

    /*
     * num and -num isolates the lowest set bit.
     * log2(...) gives the zero-based index of that bit.
     */
    return log2((num and -num).toDouble()).toInt()
}

fun main() {
    val num = 4224 // 0001 0000 1000 0000

    // Find and display the position of the first set bit
    val position = findFirstSetBitPosition(num)
    if (position == 0) {
        println("The number has no set bits (it's 0).")
    } else {
        println("The position of the first set bit is: $position")
    }
}



/*
run:

The position of the first set bit is: 7

*/

 



answered Sep 4, 2025 by avibootz
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