Project Euler: Problem 92

Euler0092.scala

package euler.zerosum

import euler.zerosum.Number._

object Euler0092 {

  def main(args: Array[String]) {
    val n = from(0).take(1000)

    println(
      n
      .par
      .map(x => {
        from(x*10000 + 1).take(10000).par.filterNot(terminateDigitChain(_) == 1).length
      })
      .sum)
  }

  def terminateDigitChain(s: Int): Int = {
    val d = sumOfSquareDigit(s)

    if (d == 1 || d == 85 || d == 58) d else terminateDigitChain(d)
  }

  def sumOfSquareDigit(n: Int): Int = {
    println(n)
    n.toString.toList.map(_.toInt - 48).fold(0)((sum, x) => sum + x * x)
  }
}