SumDigits, only more meta.

SumDigitsMeta.scala

object SumDigits {
  def maxInt = 2147483647
  
  def printResult(arg: Int){
    printResult(arg, sumDigits(arg));
  }
  def printResult(arg: Int, result: Int){
    printf("Sum of %d is %d\n", arg, result);
  }
  
  def main(args: Array[String]) {
    println("heelo [sic] world");
    
    printResult(maxInt); //46 (Int [31 bit + 1 bit for sign] max value)
    printSumDigitsGivenInitialAsMaxSum(323523)
//    printSumDigitsGivenInitialAsMaxSum(99999999);
  }

  def sumDigits(arg: Int): Int =  { 
    def absArg = scala.math.abs(arg); //As a precondition, I *could* say I only accept natural numbers. I could.

    var power: Long = 1; // All Int values accepted, power must go to 100000000000 (exceeds max Int value)
    var sizeArg = absArg % power; // 0

    // Accumulate our modulus operand [power] by measuring the results of increasing modulo ops
    while (sizeArg != absArg) {
      power = power * 10;
      sizeArg = absArg % power;
    }

    var digitSum: Int = 0;
    var argVar: Int = absArg;

    // Accumulate sum of digits
    while (power > 1) {
      // Get single-digit value from integer at [tens] place
      var digit = ((argVar - (argVar % power)) / power).toInt;
      digitSum = digitSum + digit;
      // Remove digit we just added to digitSum
      argVar = (argVar % power).toInt;
      // Go to next lower power of 10s
      power = power / 10;
    }

    // Add the last digit
    digitSum = digitSum + (arg % 10);

    return digitSum;
  } : Int
    
  // Note that for large numbers, this goes Big-O(x*x) (or something like that)
  def printSumDigitsGivenInitialAsMaxSum(arg: Int){
    def max = sumDigits(arg)
    printResult(arg, max);
    
    var foundValues = Seq[Int]();
    var current = max - 1;
    
    for(i <- (1 until arg).reverse){
      def result = sumDigits(i);
      
      while(foundValues.contains(current)){
        current = current - 1;
      }
      
      if(result <= current && foundValues.contains(result) == false){
        printResult(i, result);
        foundValues = foundValues.+:(result);
      }
    }
  }
}