if with zip and count

Hamming
Hamming in Scala 
object Hamming {

  def distance(strand1: String, strand2: String): Option[Int] = {
    if (strand1.length != strand2.length)
      return None
    Some(strand1 zip strand2 count (strand => strand._1 != strand._2))
  }
}

This approach starts by using an if statement to compare the lengths of the strands. If the lengths are not equal the function returns None.

Otherwise, the two strands are zipped together into tuples of a Char from each of the strands. So the first tuple could have the first Char from each of the strands, the second tuple would have the second Char from each of the stands, and so on. Each tuple is passed to the count() method. The lambda in the count() method compares the Chars in the tuple and adds to the count only when the two Chars are different from each other.

When the zip()method has iterated all of the tuples, the result of the count is wrapped in a Some. Since all of that is the last line in the function, the Some expression is implicitly returned from the function without needing the return keyword.

9th Oct 2024 · Found it useful?

Other Approaches to Hamming in Scala

Other ways our community solved this exercise
def distance(strand1: String, strand2: String): Option[Int] = {
  strand1.length == strand2.length match {
    case true =>
      Some(strand1 zip strand2 count (strand => strand._1 != strand._2))
    case false => None
  }
}
match with zip and count

Use match with zip and count to return the answer. 

@tailrec def distanceCount(acc: Int, s1: String, s2: String): Int = {
  s1.length match {
    case 0 => acc
    case _ =>
      distanceCount(
        (if (s1.head != s2.head) acc + 1 else acc),
        s1.tail,
        s2.tail)}}
match with recursion

Use match with recursion to return the answer.