euler for PiS Study

p002.scala

package kr.ne.outsider

object p002 extends App {
  var cache:Map[Int, Int] = Map()
  
  def fibonacci(x: Int): Int = {
    cache.get(x) match {
      case Some(t) => t
      case _ => {
        x match {
          case 0 => cache += (x -> x); x
          case 1 => cache += (x -> x); x
          case _ => {
            val temp = fibonacci(x-1) + fibonacci(x-2)
            cache += (x -> temp)
            temp
          }
          
        }
      }
    }
  }
  
  def _loop(x: Int, accum: Int): Int = {
    val temp = fibonacci(x)
    temp match {
      case a if a >= 4000000 => accum
      case a if a % 2 == 0 => _loop(x + 1, accum + temp)
      case _ => _loop(x + 1, accum)
    }
  }
  
  def time[R](block: => R): R = {
    val t0 = System.nanoTime()
    val result = block    // call-by-name
    val t1 = System.nanoTime()
    println("Elapsed time: " + (t1 - t0) + "ns")
    result
  }
  
  println(time {_loop(1, 0)}) // Elapsed time: 6742000ns
}