EX_10.scala

object Triplicate {
  def main(args: Array[String]): Unit = {

    println("Enter numbers separated by a comma")

    val nums = scala.io.StdIn.readLine()

    val arr = nums.split(",").map(x => x.toInt)

    val trip = arr.flatMap(x => List(x, x, x))

    println(s"OG Array: ${arr.toSeq}")
    println(s"Triplicated Array: ${trip.toSeq}")
  }
}

EX_5.scala

import scala.io.StdIn.{readInt, readLine}
import scala.collection.mutable.ArrayBuffer

// Java has ArrayList for a growable array
// Scala does not have ArrayList
// We instead have ArrayBuffer

object StringOp {
  def main(args: Array[String]): Unit = {
    val arrList: ArrayBuffer[String] = new ArrayBuffer()
    var cont = true

    while(cont == true) {
        println("1. Append to end")
        println("2. Insert at")
        println("3. Search an element")
        println("4. List all elements starting with given letter")

        val choice = readInt()

        choice match {
            case 1 => {
                println("String to insert?")
                val item = readLine()
                arrList.append(item)
            }
            case 2 => {
                println("String to insert?")
                val item = readLine()
                println("Insert at?")
                var pos = readInt()
                if(pos <= 0) pos = 1
                arrList.insert(pos - 1, item)
            }
            case 3 => {
                println("String to search?")
                val item = readLine()
                val pos = arrList.indexOf(item)
                if(pos != -1) println(s"It exists at position ${pos + 1}")
                else println("It does not exist.")
            }
            case 4 => {
                println("Letter to start with?")
                val item = readLine()
                val res = arrList.filter(x => x.startsWith(item))
                println(res)
            }
            case _ => {
                println("Exiting")
                cont = false
            }
        }
        // Wait for input before proceeding to next
        readLine()
    }
  }
}

EX_9.scala

object OddOrEven {
  def main(args: Array[String]) = {
    
    println("Enter numbers separated by a comma")

    val nums = scala.io.StdIn.readLine()

    val arr = nums.split(",").map(x => x.toInt)

    for (i <- 0 until arr.length) {
      for (j <- i until arr.length) {
        if (arr(j) % 2 == 0) {
          val k = arr(i);
          arr(i) = arr(j);
          arr(j) = k;
        }
      }
    }
    println(arr.toSeq);
  }
}