Project Euler: Problem 4

Euler0004.scala

object Euler0004 {

  def main(args: Array[String]): Unit = {
    println(findLargiestPalindrome(3))
  }

  private def findLargiestPalindrome(digit: Int): Int = {
    val minRange = Math.pow(10, digit-1).toInt
    val maxRange = Math.pow(10, digit).toInt
    val factors = (minRange until maxRange).toList

    findLargiestPalindrome(factors, 0)
  }

  private def findLargiestPalindrome(factors: List[Int], tempLargiest: Int): Int = {
    val palindromes = factors.map(_ * factors.last)
                             .filter(x => x.toString == x.toString.reverse)

    if(Math.pow(factors.init.last, 2) < tempLargiest){
      tempLargiest
    } else if(palindromes.nonEmpty && tempLargiest < palindromes.last){
      findLargiestPalindrome(factors.init, palindromes.last)
    } else {
      findLargiestPalindrome(factors.init, tempLargiest)
    }
  }
}