TheNextNumber.scala

import java.io.{FileReader, BufferedReader}

object TheNextNumber extends App {

  val input = new BufferedReader(new FileReader("B-small-practice.in"))
  val T: Int = input.readLine().toInt

  def nextNumber(s: String): String = {
    for (i <- (s.length-1) to 0 by -1) {
      if (s(i) > s(i-1)) {
        val front = s.substring(0, i-1)
        val arr = s.substring(i).toList
        val mid = arr.filter(j => s(i-1) < j).min
        val idx = arr.indexOf(mid)
        val end = arr.updated(idx, s(i-1)).sorted.mkString
        return front + mid + end
      }
    }
    s
  }

  for (t <- 0 until T) {
    val num = "0" + input.readLine()
    val result = BigInt(nextNumber(num))
    println(f"Case #${t + 1}: ${result}")
  }
}