EulerProject.scala

EulerProject.scala

//1
(1 to 1000).filter(x => x%3==0 || x%5==0).sum

//2
def fib: Stream[Long] = {
  def tail(h: Long, n: Long): Stream[Long] = h #:: tail(n, h + n)
  tail(0, 1)
}

//3 Largest prime factor
object Euler03 {
 
  type Factor = Long
  type Number = Long
  type Factors = List[Factor]
 
  /* Returns the largest prime factor of the given
   * number.It first computes all the prime factors of the given
   * number and then returns the largest among them.
   */
  def largestPrimeFactor (x: Number): Factor =
    primeFactors(x).max
 
 
  /* Returns the prime factors of the given number x. For instance
   * if the number x equals to 5, it returns List(2,3).
   */
  def primeFactors(x: Number): Factors = {
    val numUpToSqrt = (2L to math.sqrt(x).toLong)
    val divisibleBy = numUpToSqrt.find(x % _ == 0)
 
    divisibleBy match {
      case None =>  List(x) 
      // x is a prime number and not divisible by any
      case Some(d) => d :: primeFactors(x/d)
    }
  }
}