package kapitel_01

/**
 * Beispiel aus
 *
 * - Algorithmen und Datenstrukturen für Dummies
 *   - von Andreas Gogol-Döring und Thomas Letschert
 *   - Verlag Wiley-VCH; Oktober 2019
 *  - Kapitel 1, Das sind Algorithmen
 *
 * @author A. Gogol-Döring, Th. Letschert
 */
object AuD_01_02_GGT_App extends App {

  def GGT1(m: Int, n: Int): Int = {
    val t = (
      for (x <- 1 to 10000//Int.MaxValue;
            if (m % x) == 0 && (n % x) == 0
      ) yield x ) . max
    return t
  }

  println(GGT1(12, 18))

  def GGT2(m: Int, n: Int): Int = {
    var  t = 1
    for (x <- 1 to Math.min(m, n))
      if ((m % x) == 0 && (n % x) == 0)
        t = x
    t
  }

  println(GGT2(12, 18))

  def GGT2math1(m: Int, n: Int): Int = {
    val g =  Math.min(m, n)
    val t = (for (x <- 1 to g;
      if (m % x) == 0 && (n % x) == 0
      ) yield x) . max
    t
  }

  println(GGT2math1(12, 18))

  def GGT2math2(m: Int, n: Int): Int = {
    val g =  Math.min(m, n)
    val t = (1 to g).filter(x => (m % x) == 0 && (n % x) == 0).max
    t
  }

  println(GGT2math2(12, 18))

  def GGT2math3(m: Int, n: Int): Int =
    (1 to Math.min(m, n))
      .filter(x => (m % x) == 0 && (n % x) == 0)
      .max

  println(GGT2math3(12, 18))

  def GGT3(m: Int, n: Int): Int = {

    def isDivisor(x: Int, z:Int) : Boolean = {
      var z_t = z
      while (z_t > 0)
        z_t = z_t - x
      z_t == 0
    }

    var t = 1
    for (x <- 2 to Math.min(n, m)) if (isDivisor(x, m) && isDivisor(x, n)) t = x
    t
  }

  println(GGT3(12, 18))

}