Kadane's Algorithm in Scala

Question

Does anyone have a Scala implementation of Kadane\'s algorithm done in a functional style?

Edit Note: The definition on the link has changed in a way that invali

Answer 1

The following code returns the start and end index as well as the sum:

import scala.math.Numeric.Implicits.infixNumericOps
import scala.math.Ordering.Implicits.infixOrderingOps

case class Sub[T: Numeric](start: Index, end: Index, sum: T)

def maxSubSeq[T](arr: collection.IndexedSeq[T])(implicit n: Numeric[T]) =
  arr
    .view
    .zipWithIndex
    .scanLeft(Sub(-1, -1, n.zero)) {
      case (p, (x, i)) if p.sum > n.zero => Sub(p.start, i, p.sum + x)
      case (_, (x, i))                   => Sub(i, i, x)
    }
    .drop(1)
    .maxByOption(_.sum)