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  1. Practice
  2. Functional Programming
  3. Introduction
  4. Compute the Perimeter of a Polygon
  5. Discussions

Compute the Perimeter of a Polygon

  • hannavarapu + 3 comments
    object Solution {

  def main(args: Array[String]) {

    val N = scala.io.StdIn.readInt
    val points = scala.io.Source.stdin.getLines().take(N).map(x=>x).toList
    println(dist(points:+points.head ))

  }
  def dist(A: List[String]): Double = {
    if(A.length>=2)
      scala.math.sqrt(scala.math.pow((A(0).split(" ")(0).toDouble-A(1).split(" ")(0).toDouble),2) + scala.math.pow((A(0).split(" ")(1).toDouble-A(1).split(" ")(1).toDouble),2))+ dist(A.drop(1))
    else 0
  }
}

    This is my scala code. It gives the correct output in my system but when I run it here, it gives me this error: java.util.NoSuchElementException: head of empty list

    • Ahzaz + 0 comments

      println(dist(points:+points.head )) If points is empty, points.head throws exception

    • harjolgoo + 0 comments

      scala.io.Source.stdin.getLines() cannot read after scala.io.StdIn because of . I donot know it's a bug or a feature... you can try 

      val points = (1 to N).map(_ => scala.io.StdIn.readLine()).toList
    • shinasamuel + 1 comment

      A hack would be to read everything as val points = scala.io.Source.stdin.getLines() which is a Iterator[String] and get N as

      val N = points.next()

      • naderghanbari + 0 comments

        Actually val lines = stdin.getLines().drop(1) will give you all lines you need, dropping the first one, which is good enough for this problems. In real life, though, it's better not to do it this way.