Question

I am new to Scala and functional programming.

I was solving problem where you have to read number, and then that number of integers. After that you should calculate sum of all digits in all the integers.

Here is my code

def sumDigits(line: String) = 
    line.foldLeft(0)(_ + _.toInt - '0'.toInt)

  def main(args: Array[String]) {
    val numberOfLines = Console.readInt
    val lines = for (i <- 1 to numberOfLines) yield Console.readLine   
    println(lines.foldLeft(0)( _ + sumDigits(_)))
  }

Is there more elegant or efficient way?

Answer 1

sumDigits() can be implemented easier with sum:

def sumDigits(line: String) = line.map(_.asDigit).sum

Second foldLeft() can also be replaced with sum:

lines.map(sumDigits).sum

Which brings us to the final version (notice there is no main, instead with extend App):

object Main extends App {

    def sumDigits(line: String) = line.map(_.asDigit).sum

    val lines = for (_ <- 1 to Console.readInt) yield Console.readLine   
    println(lines.map(sumDigits).sum)

}

Or if you really want to squeeze as much as possible in one line, inline sumDigits (not recommended):

lines.map(_.map(_.asDigit).sum).sum