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  1. Practice
  2. Functional Programming
  3. Recursion
  4. String Mingling
  5. Discussions

String Mingling

  • serhii_nesteruk + 2 comments

    Hello! I wonder why is this solution is better than mine:

    def recursiveZip(l1: List[Char], l2: List[Char], acc: List[Char]): List[Char] = {
    if(l1.isEmpty) acc
    else recursiveZip(l1.tail, l2.tail, acc ++ List(l1.head, l2.head))
}

    It is tail recursive function, list concatenation has linear complexity

    • PRASHANTB1984 + 0 comments

      many compilers are optimized for tail-recursion which makes such functions less inefficient than one would normally expect them to be. For example, the tailRec keyword in Scala.

    • abhiranjanChallenge Author + 1 comment

      @serhii_nesteruk, :: has constant complexity, while ++ is linear.

      In your code you are applying ++ n times. First on the list of length 1, then 2, then 3, and so on. So overall complexity will be 

      O(1) + O(2) + ... + O(n-1) ~= O(n^2)
      • serhii_nesteruk + 0 comments

        thanks for the explanation!