Combining two lists in Scala

Question

From 2 lists of the form List[(Int, String):

l1 = List((1,\"a\"),(3,\"b\"))
l2 = List((3,\"a\"),(4,\"c\"))

how can I combine t

Answer 1

Note that with this solution, the lists are traversed twice.

val l3 = (l1 zip l2).foldRight(List[(Int, String)]()) {
  case ((firstPair @ (firstNumber, firstWord),
        secondPair @ (secondNumber, secondWord)),
        result) =>
    if (firstWord == secondWord)
      ((firstNumber + secondNumber), firstWord) :: result
    else
      firstPair :: secondPair :: result
}