weighted_selection_2.scala

// Weighted random selection in Scala 2
// You have an array of items. Each item is an unsigned integer.
// The value of each item determines its weight.
// Higher the weight, higher the chance of rolling it.

class Fortuna(items: Array[Double]) {
  private val weights = items;
  private val cumulativeWeights: Array[Double] = new Array(items.length);
  private var totalChance: Double = 0;
  for (i <- 0 until items.length) {
    cumulativeWeights(i) = totalChance + items(i);
    totalChance = totalChance + items(i);
  }
  def get(count: Int): Array[Int] = {
    val result = new Array[Int](count);
    for (i <- 0 until count) {
      result(i) = roll();
    }
    return result;
  }
  def get_with_linear_search(count: Int): Array[Int] = {
    val result = new Array[Int](count);
    for (i <- 0 until count) {
      result(i) = roll_with_linear_search();
    }
    return result;
  }
  def roll(): Int = {
    if (cumulativeWeights.length == 1) return -1;
    val rng = Math.random() * totalChance;
    var lower = 0;
    var max = cumulativeWeights.length - 1;
    var mid = ((max + lower) / 2);
    while (mid != 0 && lower <= max) {
      if (
        (cumulativeWeights(mid) > rng &&
          cumulativeWeights(mid - 1) < rng) ||
        cumulativeWeights(mid) == rng
      ) return mid;
      if (cumulativeWeights(mid) < rng) {
        lower = mid + 1;
        mid = ((max + lower) / 2);
      } else {
        max = mid - 1;
        mid = ((max + lower) / 2);
      }
    }
    return mid;
  }

  def roll_with_linear_search(): Int = {
    if (weights.length == 1) return -1;
    val rng = Math.random() * totalChance;
    var total = totalChance;
    var i = 0;
    if (totalChance == 0) {
      while (i < weights.length) {
        total = total + weights(i);
        i = i + 1;
      }
    }
    val result = Math.random() * total;
    var going = 0.0;
    i = 0;
    while (i < weights.length) {
      going = going + weights(i);
      if (result < going) {
        return i;
      }
      i = i + 1;
    }
    return (Math.random() * weights.length).toInt;
  }
}

object Test {
  val data: Array[Double] = Array(25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 11,
    11, 11, 25, 25, 25, 11, 1, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 11, 11, 11, 25, 25, 25, 11, 25, 1, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 11, 11, 11, 11, 11, 11, 11, 11, 1, 1, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 11, 11, 11, 11, 11, 11, 11,
    25, 25, 1, 1, 1, 1, 1, 1, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 11, 11,
    11, 25, 25, 11, 11, 25, 11, 1, 1, 1, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 11,
    11, 25, 1, 1, 1, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 1, 1, 25, 25, 25, 25, 1, 1, 1, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    25, 25, 25, 1, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25);

  def main(args: Array[String]) = {
    println("Woke");
    val machine = new Fortuna(data);
    println(s"${machine.get(1000).toSeq}")
    println(s"${machine.get_with_linear_search(1000).toSeq}")
  }
}

weighted_selection_3.scala

// Weighted random selection in Scala 3
// You have an array of items. Each item is an unsigned integer.
// The value of each item determines its weight.
// Higher the weight, higher the chance of rolling it.

class Fortuna(items: Array[Double]) {
  private val weights = items;
  private val cumulativeWeights: Array[Double] = new Array(items.length);
  private var totalChance: Double = 0;
  for (i <- 0 until items.length) {
    cumulativeWeights(i) = totalChance + items(i);
    totalChance = totalChance + items(i);
  }
  def get(count: Int): Array[Int] = 
    val result = new Array[Int](count);
    for (i <- 0 until count) {
        result(i) = roll();
    }
    return result;
  def get_with_linear_search(count: Int): Array[Int] = 
    val result = new Array[Int](count);
    for (i <- 0 until count) {
        result(i) = roll_with_linear_search();
    }
    return result;
  def roll(): Int = 
    if (cumulativeWeights.length == 1) return -1;
    val rng = Math.random() * totalChance;
    var lower = 0;
    var max = cumulativeWeights.length - 1;
    var mid = ((max + lower) / 2);
    while (
      mid != 0 && lower <= max
    ) {
      if (
        (cumulativeWeights(mid) > rng &&
          cumulativeWeights(mid - 1) < rng) ||
        cumulativeWeights(mid) == rng
      ) return mid;
      if (cumulativeWeights(mid) < rng) {
        lower = mid + 1;
        mid = ((max + lower) / 2);
      } else {
        max = mid - 1;
        mid = ((max + lower) / 2);
      }
    }
    return mid;
  
  def roll_with_linear_search(): Int = 
    if (weights.length == 1) return -1;
    val rng = Math.random() * totalChance;
    var total = totalChance;
    var i = 0;
    if (totalChance == 0) {
      while (i < weights.length) {
        total = total + weights(i);
        i = i + 1;
      }
    }
    val result = Math.random() * total;
    var going = 0.0;
    i = 0;
    while (i < weights.length) {
      going = going + weights(i);
      if (result < going) {
        return i;
      }
      i = i + 1;
    }
    return (Math.random() * weights.length).toInt;
  
}

val data: Array[Double] = Array(25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,11,11,11,25,25,25,11,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,11,11,11,25,25,25,11,25,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,11,11,11,11,11,11,11,11,1,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,11,11,11,11,11,11,11,25,25,1,1,1,1,1,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,11,11,11,25,25,11,11,25,11,1,1,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,11,11,25,1,1,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,1,1,25,25,25,25,1,1,1,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,1,25,25,25,25,25,25,25,25,25,25,25,25);

@main def Test() = 
    val machine = new Fortuna(data);
    println(s"${machine.get(1000).toSeq}")
    println(s"${machine.get_with_linear_search(1000).toSeq}")