euler problem 14

p014.scala

import scala.annotation.tailrec

@tailrec
def loop(n: Long, count: Int = 0): Int = {
  n match {
    case 1 => count
    case x if x % 2 == 0 => loop(x / 2, count + 1)
    case x if x % 2 == 1  => loop(3 * x  + 1, count + 1)
  }
}

(for (
  i <- 1 to 1000000
) yield (i, loop(i)) ).maxBy(_._2)