daiksy

  /**
   * http://projecteuler.net/problem=14
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2014
   */


  object collatz {
    def apply(i: Int) = calc(i :: Nil).reverse

    private def calc(xs: List[Long]): List[Long] = {

daiksy

  /**
   * http://projecteuler.net/problem=13
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2013
   */

  val xs = List(
    BigInt("37107287533902102798797998220837590246510135740250"),
    BigInt("46376937677490009712648124896970078050417018260538"),
    BigInt("74324986199524741059474233309513058123726617309629"),
    BigInt("91942213363574161572522430563301811072406154908250"),

daiksy

  /**
   * http://projecteuler.net/problem=12
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2012
   */

  def numbers(n: Long): Stream[Long] = n #:: numbers(n + 1L)

  val triangle = numbers(2L).scanLeft(1L){(a,b) => a + b }

  val divisors = (n: Long) => {

daiksy

  /**
   * http://projecteuler.net/problem=11
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2011
   */

  val xs: List[List[Int]] = List(
           List(8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8),
           List(49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 4, 56, 62, 0),
           List(81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 3, 49, 13, 36, 65),
           List(52, 70, 95, 23, 4, 60, 11, 42, 69, 24, 68, 56, 1, 32, 56, 71, 37, 2, 36, 91),

daiksy

  /**
   * http://projecteuler.net/problem=10
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2010
   */

  def isPrime(n: Long) = Iterator.from(2).takeWhile(p => p * p <= n).forall(p => n % p != 0)
  def xs = 2L until 2000000L

  val ret = xs filter isPrime sum

daiksy

  /**
   * 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

daiksy

  /**
   * http://projecteuler.net/problem=8
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%208
   */

  val s = "7316717 ... 63450" // 途中省略してます.
  val xs = s.toList.map(_.toString.toInt)

  def product(xs: List[Int], ys: List[Int]): List[Int] = {
    xs match {

daiksy

  /**
   * http://projecteuler.net/problem=7
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%207
   */

  val isPrime = (n: Int) => Iterator.from(2).takeWhile(p => p * p <= n).forall(p => n % p != 0)
  def xs(n: Int): Stream[Int] = n #:: xs(n + 1)

  val ret = xs(2).filter(isPrime).take(10001).last
  println(ret)

daiksy

  /**
   * http://projecteuler.net/problem=6
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%206
   */
  val xs = 1 to 100
  import scala.math.pow
  val ret = pow(xs.sum, 2).toInt - xs.map(pow(_, 2)).sum.toInt
  println(ret)

daiksy

  /**
   * http://projecteuler.net/problem=5
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%205
   */
  def findAnswer(n: Int): Int = {
    val l = List.range(1, 21, + 1)
    if (l.forall(n % _ == 0)) {
      n
    } else {
      findAnswer(n + 1)