Project Euler Problem 9

problem9.scala

  /**
   * http://projecteuler.net/problem=9
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%209
   */

  def triplesOfTotal1000: List[(Int, Int, Int)] = {

    def search(a: Int, b: Int, c: Int, xs: List[(Int, Int, Int)]): List[(Int, Int, Int)] = {
      val ys = if (a + b + c == 1000) (a, b, c) :: xs else xs

      (a, b, c) match {
        case (_, _, 997) => search(a, b + 1, b + 2, ys)
        case (_, 499, _) => search(a + 1, a + 2, a + 3, ys)
        case (333, _, _) => ys
        case _ => search(a, b, c + 1, ys)
      }
    }

    search(1, 2, 3, Nil)
  }

  import scala.math.pow
  val t = triplesOfTotal1000.find {case (a, b, c) => pow(a, 2) + pow(b, 2) == pow(c, 2)}.get

  val ret = t._1 * t._2 * t._3

  println(ret)