fromRange2.scala

import scala.collection.immutable.BitSet

def fromRange(xs: List[(Int, Int)]): BitSet = {
  val range = BitSet.newBuilder
  xs.foreach {
    case (start, end) =>
      range ++= BitSet((start to end): _*)
  }
  range.result
}

val t1 = List((14, 20), (60, 80), (180, 270))
val r1 = fromRange(t1)
println(r1)

def fromRange2(xs: List[(Int, Int)]): BitSet = {
  val n = 64
  val max = xs.maxBy(_._2)._2
  val mask = Array.ofDim[Long](max / n + 1)
  xs.foreach {
    case (start, end) => {
      var i = start
      while(i <= end) {
        val idx = i / n
        mask.update(
          idx,
          mask(idx) | (1L << (i - (idx * n)))
        )
        i += 1
      }
    }
  }
  BitSet.fromBitMaskNoCopy(mask)
}

val r2 = fromRange2(t1)
println(r2)

r1 == r2