Question

How to set specific bits and find the set bits indexes in Kotlin

Answer 1

const val BIT_SIZE = 16

// Print binary representation of the bits
fun printBinary(bits: Short) {
    val binary = bits.toInt().toString(2).padStart(BIT_SIZE, '0')
    println(binary)
}

// Find the first set bit (least significant)
fun findFirstSetBit(bits: Short): Int? {
    for (i in 0 until BIT_SIZE) {
        if ((bits.toInt() shr i) and 1 == 1) return i
    }
    return null
}

fun printSetBitIndexes(bits: Short) {
    val indexes = (0 until BIT_SIZE).filter { (bits.toInt() shr it) and 1 == 1 }
    println(indexes.joinToString(" "))
}

fun main() {
    var bits: Short = 0
    bits = (bits.toInt() or (1 shl 3)).toShort()
    bits = (bits.toInt() or (1 shl 5)).toShort()
    bits = (bits.toInt() or (1 shl 11)).toShort()
    bits = (bits.toInt() or (1 shl 14)).toShort()

    printBinary(bits)

    val first = findFirstSetBit(bits)
    println("First set bit at index: ${first ?: "None"}")

    println("All the set bits indexes:")
    printSetBitIndexes(bits)
}



/*
run:

0100100000101000
First set bit at index: 3
All the set bits indexes:
3 5 11 14

*/

 

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