Question

How to generate non‑overlapping random ranges (start,end),(start,end) in Scala

Answer 1

import scala.util.Random

object NonOverlappingRanges {

  def generateNonOverlappingRandomRanges(begin: Int, end: Int, numRanges: Int): List[(Int, Int)] = {
    val count = numRanges * 2

    // ------------------------------------------------------------
    // Generate unique random points in [begin, end)
    // The random numbers are chaotic and NOT sorted
    // ------------------------------------------------------------
    val rng = new Random()
    val pointsSet = Iterator
      .continually(begin + rng.nextInt(end - begin))
      .distinct                      // ensure uniqueness
      .take(count)                   // collect exactly count unique points
      .toList

    // ------------------------------------------------------------
    // Sort the points
    // Only AFTER sorting do the ranges become increasing
    // and automatically non‑overlapping
    // ------------------------------------------------------------
    val sortedPoints = pointsSet.sorted

    // ------------------------------------------------------------
    // Pair adjacent sorted points into (start, end) ranges
    // ------------------------------------------------------------
    sortedPoints
      .grouped(2)
      .collect { case List(a, b) => (a, b) }
      .toList
  }

  def main(args: Array[String]): Unit = {
    val start = 1
    val end = 500
    val numRanges = 8

    val ranges = generateNonOverlappingRandomRanges(start, end, numRanges)
    ranges.foreach { case (s, e) => println(s"($s, $e)") }
  }
}
 
 
 
 
/*
run:
 
(41, 46)
(47, 56)
(69, 93)
(112, 130)
(131, 154)
(233, 251)
(317, 386)
(392, 484)
 
*/

 

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