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

1 Answer

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object FirstSetBit {

  // Function to find the position of the first set bit
  def findFirstSetBitPosition(num: Int): Int = {
    // Edge case: If the number is 0, there are no set bits
    if (num == 0) {
      0 // Return 0 to indicate no set bit
    } else {
      /*
       * num & -num isolates the lowest set bit.
       * log2(...) gives the zero-based index of that bit.
       */
      (math.log(num & -num) / math.log(2)).toInt
    }
  }

  def main(args: Array[String]): Unit = {
    val num = 4224 // Binary: 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(s"The position of the first set bit is: $position")
    }
  }
}



/*
run:

The position of the first set bit is: 7

*/



/*
run:

swap() left: 0 right: 8
left: 1
right: 7
swap() left: 2 right: 6
left: 3
swap() left: 4 right: 5
Sorted array: 0 0 0 0 0 1 1 1 1

*/

 



answered Sep 4, 2025 by avibootz
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