https://www.hackerrank.com/challenges/pairs

pairs.scala

/**
 * https://www.hackerrank.com/challenges/pairs
 */
object Solution {

  def main(args: Array[String]): Unit = {
    val (n, k) = readNK(readLine())
    val numbers = readNumbers(readLine())

    var answer = 0
    for (num <- numbers) {
      if (numbers.contains(num + k)) {
        answer += 1
      }
    }
    println(answer)
  }

  private def readNK(line: String): (Int, Int) = {
    val temp = line.split(" ")
    val N = temp(0).toInt
    val K = temp(1).toInt
    (N, K)
  }

  private def readNumbers(line: String): Set[Int] = {
    val result = collection.mutable.Set.empty[Int]
    val nums = line.split(" ")
    for (num <- nums) {
      result += num.toInt
    }
    result.toSet
  }
}