projecteuler

Euler.scala

object Euler {
  // http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%205
  def main(args: Array[String]) {
//    val r1 = test(10)
    val r = (1L to 20L).reduceLeft(lcm)

    println(r)
  }

//  def test(n: Int) = (20 to Int.MaxValue).find(x => (2 to n).forall(x % _ == 0))

  // 最小公倍数(least common multiple)
  def lcm(a: Long, b: Long): Long =
    a * b / gcd(a, b)

  // 最大公約数(greatest common divisor)
  // Euclidean Algorithm
  @scala.annotation.tailrec
  def gcd(a: Long, b: Long): Long =
    if (b == 0) a
    else gcd(b, a % b)
}