Prints out steps of multiplicative persistence

MultiplicativePersistence.swift

func multiplicativePersistence(of int: UInt64, step: Int = 1) {
  if step == 1 {
    print("Step 0:", int)
  }
  var mutatingInt = int
  var remainder: UInt64

  var currentValue: UInt64 = 1  
  while mutatingInt != 0 {
    (mutatingInt, remainder) = mutatingInt.quotientAndRemainder(dividingBy: 10)
    currentValue *= UInt64(remainder)
  }
  print("Step \(step):", currentValue)
  if currentValue.quotientAndRemainder(dividingBy: 10).quotient == 0 {
    return
  } else {
    multiplicativePersistence(of: currentValue, step: step+1)
  }
}

multiplicativePersistence(of: 888888)